Remove content::NotificationObserver dependency from most Prefs code.

Instead of using content::NotificationObserver, introduce specific
type-safe observer classes and update users to use them.  In a very
large number of cases this was the users' only reason for being a
content::NotificationObserver and they would have a lot of
boiler-plate code such as a DCHECK on the notification type and
unpacking of the generic NotificationDetails types, so this change
removes a bunch of boilerplate and introduces more type safety.

This is part of enabling more of the Prefs code to live in
base/prefs/.

TBR=ben@chromium.org,brettw@chromium.org
BUG=155525


Review URL: https://chromiumcodereview.appspot.com/11345008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@165414 0039d316-1c4b-4281-b951-d872f2087c98

194 files changed, 1437 insertions, 1516 deletions

diff --git a/base/base.gyp b/base/base.gyp
index 699fe46..14460d4 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -329,6 +329,7 @@
         'prefs/pref_value_map.h',
         'prefs/public/pref_change_registrar.cc',
         'prefs/public/pref_change_registrar.h',
+        'prefs/public/pref_observer.h',
         'prefs/public/pref_service_base.h',
         'prefs/value_map_pref_store.cc',
         'prefs/value_map_pref_store.h',
diff --git a/base/prefs/public/pref_change_registrar.cc b/base/prefs/public/pref_change_registrar.cc
index e7a9791..3f94b04 100644
--- a/base/prefs/public/pref_change_registrar.cc
+++ b/base/prefs/public/pref_change_registrar.cc
@@ -22,8 +22,7 @@ void PrefChangeRegistrar::Init(PrefServiceBase* service) {
   service_ = service;
 }
 
-void PrefChangeRegistrar::Add(const char* path,
-                              content::NotificationObserver* obs) {
+void PrefChangeRegistrar::Add(const char* path, PrefObserver* obs) {
   if (!service_) {
     NOTREACHED();
     return;
@@ -37,8 +36,7 @@ void PrefChangeRegistrar::Add(const char* path,
   service_->AddPrefObserver(path, obs);
 }
 
-void PrefChangeRegistrar::Remove(const char* path,
-                                 content::NotificationObserver* obs) {
+void PrefChangeRegistrar::Remove(const char* path, PrefObserver* obs) {
   if (!service_) {
     NOTREACHED();
     return;
diff --git a/base/prefs/public/pref_change_registrar.h b/base/prefs/public/pref_change_registrar.h
index a7e1eab..f3abd98 100644
--- a/base/prefs/public/pref_change_registrar.h
+++ b/base/prefs/public/pref_change_registrar.h
@@ -11,12 +11,9 @@
 #include "base/basictypes.h"
 #include "base/prefs/base_prefs_export.h"
 
+class PrefObserver;
 class PrefServiceBase;
 
-namespace content {
-class NotificationObserver;
-}
-
 // Automatically manages the registration of one or more pref change observers
 // with a PrefStore. Functions much like NotificationRegistrar, but specifically
 // manages observers of preference changes. When the Registrar is destroyed,
@@ -34,13 +31,11 @@ class BASE_PREFS_EXPORT PrefChangeRegistrar {
   // object. All registered observers will be automatically unregistered
   // when the registrar's destructor is called unless the observer has been
   // explicitly removed by a call to Remove beforehand.
-  void Add(const char* path,
-           content::NotificationObserver* obs);
+  void Add(const char* path, PrefObserver* obs);
 
   // Removes a preference observer that has previously been added with a call to
   // Add.
-  void Remove(const char* path,
-              content::NotificationObserver* obs);
+  void Remove(const char* path, PrefObserver* obs);
 
   // Removes all observers that have been previously added with a call to Add.
   void RemoveAll();
@@ -55,8 +50,7 @@ class BASE_PREFS_EXPORT PrefChangeRegistrar {
   bool IsManaged();
 
  private:
-  typedef std::pair<std::string, content::NotificationObserver*>
-      ObserverRegistration;
+  typedef std::pair<std::string, PrefObserver*> ObserverRegistration;
 
   std::set<ObserverRegistration> observers_;
   PrefServiceBase* service_;
diff --git a/base/prefs/public/pref_change_registrar_unittest.cc b/base/prefs/public/pref_change_registrar_unittest.cc
index 491d7db..f860602 100644
--- a/base/prefs/public/pref_change_registrar_unittest.cc
+++ b/base/prefs/public/pref_change_registrar_unittest.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/test/base/testing_pref_service.h"
@@ -18,6 +19,14 @@ using testing::Eq;
 
 namespace {
 
+// TODO(joi): Use PrefObserverMock once it moves to base/prefs/.
+class MockPrefObserver : public PrefObserver {
+ public:
+  virtual ~MockPrefObserver() {}
+
+  MOCK_METHOD2(OnPreferenceChanged, void(PrefServiceBase*, const std::string&));
+};
+
 // A mock provider that allows us to capture pref observer changes.
 class MockPrefService : public TestingPrefService {
  public:
@@ -25,9 +34,9 @@ class MockPrefService : public TestingPrefService {
   virtual ~MockPrefService() {}
 
   MOCK_METHOD2(AddPrefObserver,
-               void(const char*, content::NotificationObserver*));
+               void(const char*, PrefObserver*));
   MOCK_METHOD2(RemovePrefObserver,
-               void(const char*, content::NotificationObserver*));
+               void(const char*, PrefObserver*));
 };
 
 }  // namespace
@@ -40,17 +49,17 @@ class PrefChangeRegistrarTest : public testing::Test {
  protected:
   virtual void SetUp();
 
-  content::NotificationObserver* observer() const { return observer_.get(); }
+  PrefObserver* observer() const { return observer_.get(); }
   MockPrefService* service() const { return service_.get(); }
 
  private:
   scoped_ptr<MockPrefService> service_;
-  scoped_ptr<content::MockNotificationObserver> observer_;
+  scoped_ptr<MockPrefObserver> observer_;
 };
 
 void PrefChangeRegistrarTest::SetUp() {
   service_.reset(new MockPrefService());
-  observer_.reset(new content::MockNotificationObserver());
+  observer_.reset(new MockPrefObserver());
 }
 
 TEST_F(PrefChangeRegistrarTest, AddAndRemove) {
@@ -137,7 +146,7 @@ class ObserveSetOfPreferencesTest : public testing::Test {
   }
 
   PrefChangeRegistrar* CreatePrefChangeRegistrar(
-        content::NotificationObserver* observer) {
+      PrefObserver* observer) {
     PrefChangeRegistrar* pref_set = new PrefChangeRegistrar();
     pref_set->Init(pref_service_.get());
     pref_set->Add(prefs::kHomePage, observer);
@@ -180,27 +189,23 @@ TEST_F(ObserveSetOfPreferencesTest, Observe) {
   using testing::_;
   using testing::Mock;
 
-  content::MockNotificationObserver observer;
+  MockPrefObserver observer;
   scoped_ptr<PrefChangeRegistrar> pref_set(
       CreatePrefChangeRegistrar(&observer));
 
-  EXPECT_CALL(observer,
-              Observe(int(chrome::NOTIFICATION_PREF_CHANGED),
-                      content::Source<PrefService>(pref_service_.get()),
-                      PrefNameDetails(prefs::kHomePage)));
+  EXPECT_CALL(observer, OnPreferenceChanged(pref_service_.get(),
+                                            prefs::kHomePage));
   pref_service_->SetUserPref(prefs::kHomePage,
                              Value::CreateStringValue("http://crbug.com"));
   Mock::VerifyAndClearExpectations(&observer);
 
-  EXPECT_CALL(observer,
-              Observe(int(chrome::NOTIFICATION_PREF_CHANGED),
-                      content::Source<PrefService>(pref_service_.get()),
-                      PrefNameDetails(prefs::kHomePageIsNewTabPage)));
+  EXPECT_CALL(observer, OnPreferenceChanged(pref_service_.get(),
+                                            prefs::kHomePageIsNewTabPage));
   pref_service_->SetUserPref(prefs::kHomePageIsNewTabPage,
                              Value::CreateBooleanValue(true));
   Mock::VerifyAndClearExpectations(&observer);
 
-  EXPECT_CALL(observer, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(observer, OnPreferenceChanged(_, _)).Times(0);
   pref_service_->SetUserPref(prefs::kApplicationLocale,
                              Value::CreateStringValue("en_US.utf8"));
   Mock::VerifyAndClearExpectations(&observer);
diff --git a/base/prefs/public/pref_observer.h b/base/prefs/public/pref_observer.h
new file mode 100644
index 0000000..2692243
--- /dev/null
+++ b/base/prefs/public/pref_observer.h
@@ -0,0 +1,19 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_PREFS_PUBLIC_PREF_OBSERVER_H_
+#define BASE_PREFS_PUBLIC_PREF_OBSERVER_H_
+
+#include <string>
+
+class PrefServiceBase;
+
+// TODO(joi): Switch to base::Callback and remove this.
+class PrefObserver {
+ public:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) = 0;
+};
+
+#endif  // BASE_PREFS_PUBLIC_PREF_OBSERVER_H_
diff --git a/base/prefs/public/pref_service_base.h b/base/prefs/public/pref_service_base.h
index aa5b3fd..131d221 100644
--- a/base/prefs/public/pref_service_base.h
+++ b/base/prefs/public/pref_service_base.h
@@ -20,7 +20,6 @@
 
 namespace content {
 class BrowserContext;
-class NotificationObserver;
 }
 
 namespace subtle {
@@ -28,6 +27,7 @@ class PrefMemberBase;
 }
 
 class FilePath;
+class PrefObserver;
 class Profile;
 class TabContents;
 
@@ -259,14 +259,12 @@ class PrefServiceBase {
   // These are protected so they can only be accessed by the friend
   // classes listed above.
   //
-  // If the pref at the given path changes, we call the observer's Observe
-  // method with PREF_CHANGED. Note that observers should not call these methods
-  // directly but rather use a PrefChangeRegistrar to make sure the observer
-  // gets cleaned up properly.
-  virtual void AddPrefObserver(const char* path,
-                               content::NotificationObserver* obs) = 0;
-  virtual void RemovePrefObserver(const char* path,
-                                  content::NotificationObserver* obs) = 0;
+  // If the pref at the given path changes, we call the observer's
+  // OnPreferenceChanged method. Note that observers should not call
+  // these methods directly but rather use a PrefChangeRegistrar to
+  // make sure the observer gets cleaned up properly.
+  virtual void AddPrefObserver(const char* path, PrefObserver* obs) = 0;
+  virtual void RemovePrefObserver(const char* path, PrefObserver* obs) = 0;
 };
 
 #endif  // BASE_PREFS_PUBLIC_PREF_SERVICE_BASE_H_
diff --git a/chrome/browser/api/prefs/pref_member.cc b/chrome/browser/api/prefs/pref_member.cc
index 46f2aa6..e81b13a 100644
--- a/chrome/browser/api/prefs/pref_member.cc
+++ b/chrome/browser/api/prefs/pref_member.cc
@@ -8,7 +8,6 @@
 #include "base/location.h"
 #include "base/prefs/public/pref_service_base.h"
 #include "base/value_conversions.h"
-#include "chrome/common/chrome_notification_types.h"
 
 using base::MessageLoopProxy;
 
@@ -26,7 +25,7 @@ PrefMemberBase::~PrefMemberBase() {
 
 void PrefMemberBase::Init(const char* pref_name,
                           PrefServiceBase* prefs,
-                          content::NotificationObserver* observer) {
+                          PrefObserver* observer) {
   DCHECK(pref_name);
   DCHECK(prefs);
   DCHECK(pref_name_.empty());  // Check that Init is only called once.
@@ -57,14 +56,12 @@ void PrefMemberBase::MoveToThread(
   internal()->MoveToThread(message_loop);
 }
 
-void PrefMemberBase::Observe(int type,
-                             const content::NotificationSource& source,
-                             const content::NotificationDetails& details) {
+void PrefMemberBase::OnPreferenceChanged(PrefServiceBase* service,
+                                         const std::string& pref_name) {
   VerifyValuePrefName();
-  DCHECK(chrome::NOTIFICATION_PREF_CHANGED == type);
   UpdateValueFromPref();
   if (!setting_value_ && observer_)
-    observer_->Observe(type, source, details);
+    observer_->OnPreferenceChanged(service, pref_name);
 }
 
 void PrefMemberBase::UpdateValueFromPref() const {
diff --git a/chrome/browser/api/prefs/pref_member.h b/chrome/browser/api/prefs/pref_member.h
index 18a2129..7843693 100644
--- a/chrome/browser/api/prefs/pref_member.h
+++ b/chrome/browser/api/prefs/pref_member.h
@@ -32,14 +32,14 @@
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop_proxy.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/values.h"
-#include "content/public/browser/notification_observer.h"
 
 class PrefServiceBase;
 
 namespace subtle {
 
-class PrefMemberBase : public content::NotificationObserver {
+class PrefMemberBase : public PrefObserver {
  protected:
   class Internal : public base::RefCountedThreadSafe<Internal> {
    public:
@@ -91,7 +91,7 @@ class PrefMemberBase : public content::NotificationObserver {
 
   // See PrefMember<> for description.
   void Init(const char* pref_name, PrefServiceBase* prefs,
-            content::NotificationObserver* observer);
+            PrefObserver* observer);
 
   virtual void CreateInternal() const = 0;
 
@@ -100,10 +100,9 @@ class PrefMemberBase : public content::NotificationObserver {
 
   void MoveToThread(const scoped_refptr<base::MessageLoopProxy>& message_loop);
 
-  // content::NotificationObserver
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   void VerifyValuePrefName() const {
     DCHECK(!pref_name_.empty());
@@ -127,7 +126,7 @@ class PrefMemberBase : public content::NotificationObserver {
  private:
   // Ordered the members to compact the class instance.
   std::string pref_name_;
-  content::NotificationObserver* observer_;
+  PrefObserver* observer_;
   PrefServiceBase* prefs_;
 
  protected:
@@ -153,7 +152,7 @@ class PrefMember : public subtle::PrefMemberBase {
   // don't want any notifications of changes.
   // This method should only be called on the UI thread.
   void Init(const char* pref_name, PrefServiceBase* prefs,
-            content::NotificationObserver* observer) {
+            PrefObserver* observer) {
     subtle::PrefMemberBase::Init(pref_name, prefs, observer);
   }
 
diff --git a/chrome/browser/api/prefs/pref_member_unittest.cc b/chrome/browser/api/prefs/pref_member_unittest.cc
index 67a5159..3539322 100644
--- a/chrome/browser/api/prefs/pref_member_unittest.cc
+++ b/chrome/browser/api/prefs/pref_member_unittest.cc
@@ -77,21 +77,17 @@ class GetPrefValueCallback
   bool value_;
 };
 
-class PrefMemberTestClass : public content::NotificationObserver {
+class PrefMemberTestClass : public PrefObserver {
  public:
   explicit PrefMemberTestClass(PrefService* prefs)
       : observe_cnt_(0), prefs_(prefs) {
     str_.Init(kStringPref, prefs, this);
   }
 
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) {
-    DCHECK(chrome::NOTIFICATION_PREF_CHANGED == type);
-    PrefService* prefs_in = content::Source<PrefService>(source).ptr();
-    EXPECT_EQ(prefs_in, prefs_);
-    std::string* pref_name_in = content::Details<std::string>(details).ptr();
-    EXPECT_EQ(*pref_name_in, kStringPref);
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE {
+    EXPECT_EQ(service, prefs_);
+    EXPECT_EQ(pref_name, kStringPref);
     EXPECT_EQ(str_.GetValue(), prefs_->GetString(kStringPref));
     ++observe_cnt_;
   }
diff --git a/chrome/browser/autofill/autofill_manager.cc b/chrome/browser/autofill/autofill_manager.cc
index f9dfd82..132d4ce 100644
--- a/chrome/browser/autofill/autofill_manager.cc
+++ b/chrome/browser/autofill/autofill_manager.cc
@@ -290,14 +290,10 @@ void AutofillManager::RenderViewCreated(content::RenderViewHost* host) {
   UpdatePasswordGenerationState(host, true);
 }
 
-void AutofillManager::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void AutofillManager::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  std::string* pref = content::Details<std::string>(details).ptr();
-  DCHECK(prefs::kPasswordGenerationEnabled == *pref);
+  DCHECK(prefs::kPasswordGenerationEnabled == pref_name);
   UpdatePasswordGenerationState(web_contents()->GetRenderViewHost(), false);
 }
 
diff --git a/chrome/browser/autofill/autofill_manager.h b/chrome/browser/autofill/autofill_manager.h
index 4be3a4f5..af42fbe 100644
--- a/chrome/browser/autofill/autofill_manager.h
+++ b/chrome/browser/autofill/autofill_manager.h
@@ -18,6 +18,7 @@
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string16.h"
 #include "base/time.h"
 #include "chrome/browser/api/sync/profile_sync_service_observer.h"
@@ -25,7 +26,6 @@
 #include "chrome/browser/autofill/autofill_download.h"
 #include "chrome/browser/autofill/field_types.h"
 #include "chrome/browser/autofill/form_structure.h"
-#include "content/public/browser/notification_observer.h"
 #include "content/public/browser/web_contents_observer.h"
 
 class AutofillExternalDelegate;
@@ -64,10 +64,10 @@ class Message;
 
 // Manages saving and restoring the user's personal information entered into web
 // forms.
-class AutofillManager : public content::NotificationObserver,
-                        public content::WebContentsObserver,
+class AutofillManager : public content::WebContentsObserver,
                         public AutofillDownloadManager::Observer,
                         public ProfileSyncServiceObserver,
+                        public PrefObserver,
                         public base::RefCounted<AutofillManager> {
  public:
   static void CreateForWebContentsAndDelegate(
@@ -191,10 +191,9 @@ class AutofillManager : public content::NotificationObserver,
   // Register as an observer with the sync service.
   void RegisterWithSyncService();
 
-  // content::NotificationObserver override
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Determines what the current state of password generation is, and if it has
   // changed from |password_generation_enabled_|. If it has changed or if
diff --git a/chrome/browser/background/background_mode_manager.cc b/chrome/browser/background/background_mode_manager.cc
index 4fd087c..b77ba7e 100644
--- a/chrome/browser/background/background_mode_manager.cc
+++ b/chrome/browser/background/background_mode_manager.cc
@@ -284,11 +284,6 @@ void BackgroundModeManager::Observe(
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED:
-      DCHECK(*content::Details<std::string>(details).ptr() ==
-             prefs::kBackgroundModeEnabled);
-      OnBackgroundModeEnabledPrefChanged();
-      break;
     case chrome::NOTIFICATION_EXTENSIONS_READY:
       // Extensions are loaded, so we don't need to manually keep the browser
       // process alive any more when running in no-startup-window mode.
@@ -341,6 +336,12 @@ void BackgroundModeManager::Observe(
   }
 }
 
+void BackgroundModeManager::OnPreferenceChanged(PrefServiceBase* service,
+                                                const std::string& pref_name) {
+  DCHECK(pref_name == prefs::kBackgroundModeEnabled);
+  OnBackgroundModeEnabledPrefChanged();
+}
+
 void BackgroundModeManager::OnBackgroundModeEnabledPrefChanged() {
   if (IsBackgroundModePrefEnabled())
     EnableBackgroundMode();
diff --git a/chrome/browser/background/background_mode_manager.h b/chrome/browser/background/background_mode_manager.h
index 5a3db331..2cb8a78 100644
--- a/chrome/browser/background/background_mode_manager.h
+++ b/chrome/browser/background/background_mode_manager.h
@@ -9,6 +9,7 @@
 
 #include "base/gtest_prod_util.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/background/background_application_list_model.h"
 #include "chrome/browser/profiles/profile_info_cache_observer.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
@@ -47,6 +48,7 @@ class BackgroundModeManager
     : public content::NotificationObserver,
       public BackgroundApplicationListModel::Observer,
       public ProfileInfoCacheObserver,
+      public PrefObserver,
       public ui::SimpleMenuModel::Delegate {
  public:
   BackgroundModeManager(CommandLine* command_line,
@@ -158,6 +160,10 @@ class BackgroundModeManager
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Called when the kBackgroundModeEnabled preference changes.
   void OnBackgroundModeEnabledPrefChanged();
 
diff --git a/chrome/browser/browser_process_impl.cc b/chrome/browser/browser_process_impl.cc
index 7cb72c1..aacfea08 100644
--- a/chrome/browser/browser_process_impl.cc
+++ b/chrome/browser/browser_process_impl.cc
@@ -610,20 +610,14 @@ safe_browsing::ClientSideDetectionService*
   return NULL;
 }
 
-void BrowserProcessImpl::Observe(int type,
-                                 const content::NotificationSource& source,
-                                 const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* pref = content::Details<std::string>(details).ptr();
-    if (*pref == prefs::kDefaultBrowserSettingEnabled) {
-      ApplyDefaultBrowserPolicy();
-    } else if (*pref == prefs::kDisabledSchemes) {
-      ApplyDisabledSchemesPolicy();
-    } else if (*pref == prefs::kAllowCrossOriginAuthPrompt) {
-      ApplyAllowCrossOriginAuthPromptPolicy();
-    }
-  } else {
-    NOTREACHED();
+void BrowserProcessImpl::OnPreferenceChanged(PrefServiceBase* service,
+                                             const std::string& pref) {
+  if (pref == prefs::kDefaultBrowserSettingEnabled) {
+    ApplyDefaultBrowserPolicy();
+  } else if (pref == prefs::kDisabledSchemes) {
+    ApplyDisabledSchemesPolicy();
+  } else if (pref == prefs::kAllowCrossOriginAuthPrompt) {
+    ApplyAllowCrossOriginAuthPromptPolicy();
   }
 }
 
diff --git a/chrome/browser/browser_process_impl.h b/chrome/browser/browser_process_impl.h
index 304cd7a..5f18e62 100644
--- a/chrome/browser/browser_process_impl.h
+++ b/chrome/browser/browser_process_impl.h
@@ -17,10 +17,10 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/threading/non_thread_safe.h"
 #include "base/timer.h"
 #include "chrome/browser/browser_process.h"
-#include "content/public/browser/notification_observer.h"
 
 class ChromeNetLog;
 class ChromeResourceDispatcherHostDelegate;
@@ -43,7 +43,7 @@ class PolicyService;
 // Real implementation of BrowserProcess that creates and returns the services.
 class BrowserProcessImpl : public BrowserProcess,
                            public base::NonThreadSafe,
-                           public content::NotificationObserver {
+                           public PrefObserver {
  public:
   // |local_state_task_runner| must be a shutdown-blocking task runner.
   BrowserProcessImpl(base::SequencedTaskRunner* local_state_task_runner,
@@ -120,10 +120,9 @@ class BrowserProcessImpl : public BrowserProcess,
   virtual CRLSetFetcher* crl_set_fetcher() OVERRIDE;
   virtual BookmarkPromptController* bookmark_prompt_controller() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   void CreateMetricsService();
diff --git a/chrome/browser/captive_portal/captive_portal_service.cc b/chrome/browser/captive_portal/captive_portal_service.cc
index d6a013c..b2cce55 100644
--- a/chrome/browser/captive_portal/captive_portal_service.cc
+++ b/chrome/browser/captive_portal/captive_portal_service.cc
@@ -271,14 +271,10 @@ void CaptivePortalService::OnPortalDetectionCompleted(
   OnResult(result);
 }
 
-void CaptivePortalService::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void CaptivePortalService::OnPreferenceChanged(PrefServiceBase* service,
+                                               const std::string& pref_name) {
   DCHECK(CalledOnValidThread());
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(std::string(prefs::kAlternateErrorPagesEnabled),
-            *content::Details<std::string>(details).ptr());
+  DCHECK_EQ(std::string(prefs::kAlternateErrorPagesEnabled), pref_name);
   UpdateEnabledState();
 }
 
diff --git a/chrome/browser/captive_portal/captive_portal_service.h b/chrome/browser/captive_portal/captive_portal_service.h
index 82b3d71..35badc4 100644
--- a/chrome/browser/captive_portal/captive_portal_service.h
+++ b/chrome/browser/captive_portal/captive_portal_service.h
@@ -7,13 +7,13 @@
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/threading/non_thread_safe.h"
 #include "base/time.h"
 #include "base/timer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/captive_portal/captive_portal_detector.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
-#include "content/public/browser/notification_observer.h"
 #include "googleurl/src/gurl.h"
 #include "net/base/backoff_entry.h"
 
@@ -29,7 +29,7 @@ namespace captive_portal {
 // be accessed on the UI thread.
 // Design doc: https://docs.google.com/document/d/1k-gP2sswzYNvryu9NcgN7q5XrsMlUdlUdoW9WRaEmfM/edit
 class CaptivePortalService : public ProfileKeyedService,
-                             public content::NotificationObserver,
+                             public PrefObserver,
                              public base::NonThreadSafe {
  public:
   enum TestingState {
@@ -116,11 +116,9 @@ class CaptivePortalService : public ProfileKeyedService,
   void OnPortalDetectionCompleted(
       const CaptivePortalDetector::Results& results);
 
-  // content::NotificationObserver:
-  virtual void Observe(
-      int type,
-      const content::NotificationSource& source,
-      const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // ProfileKeyedService:
   virtual void Shutdown() OVERRIDE;
diff --git a/chrome/browser/chromeos/audio/audio_handler.cc b/chrome/browser/chromeos/audio/audio_handler.cc
index f9d9999..f78657f 100644
--- a/chrome/browser/chromeos/audio/audio_handler.cc
+++ b/chrome/browser/chromeos/audio/audio_handler.cc
@@ -19,7 +19,6 @@
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
-#include "content/public/browser/notification_service.h"
 
 using std::max;
 using std::min;
@@ -161,18 +160,11 @@ void AudioHandler::RemoveVolumeObserver(VolumeObserver* observer) {
   volume_observers_.RemoveObserver(observer);
 }
 
-void AudioHandler::Observe(int type,
-                           const content::NotificationSource& source,
-                           const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    if (*pref_name == prefs::kAudioOutputAllowed ||
-        *pref_name == prefs::kAudioCaptureAllowed) {
-      ApplyAudioPolicy();
-    }
-  } else {
-    NOTREACHED() << "Unexpected notification type : " << type;
-  }
+void AudioHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                       const std::string& pref_name) {
+  DCHECK(pref_name == prefs::kAudioOutputAllowed ||
+         pref_name == prefs::kAudioCaptureAllowed);
+  ApplyAudioPolicy();
 }
 
 AudioHandler::AudioHandler(AudioMixer* mixer)
diff --git a/chrome/browser/chromeos/audio/audio_handler.h b/chrome/browser/chromeos/audio/audio_handler.h
index ecb9f57a..1b77f9f 100644
--- a/chrome/browser/chromeos/audio/audio_handler.h
+++ b/chrome/browser/chromeos/audio/audio_handler.h
@@ -9,11 +9,8 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/threading/thread.h"
-#include "content/public/browser/notification_details.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
-#include "content/public/browser/notification_source.h"
 
 template <typename T> struct DefaultSingletonTraits;
 
@@ -24,7 +21,7 @@ namespace chromeos {
 
 class AudioMixer;
 
-class AudioHandler : public content::NotificationObserver {
+class AudioHandler : public PrefObserver {
  public:
   class VolumeObserver {
    public:
@@ -76,10 +73,9 @@ class AudioHandler : public content::NotificationObserver {
   void AddVolumeObserver(VolumeObserver* observer);
   void RemoveVolumeObserver(VolumeObserver* observer);
 
-  // Overridden from content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   // Defines the delete on exit Singleton traits we like.  Best to have this
@@ -107,7 +103,6 @@ class AudioHandler : public content::NotificationObserver {
   PrefService* local_state_;  // not owned
 
   PrefChangeRegistrar pref_change_registrar_;
-  content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioHandler);
 };
diff --git a/chrome/browser/chromeos/drive/drive_file_system.cc b/chrome/browser/chromeos/drive/drive_file_system.cc
index 94aedf8..98cd149 100644
--- a/chrome/browser/chromeos/drive/drive_file_system.cc
+++ b/chrome/browser/chromeos/drive/drive_file_system.cc
@@ -2140,21 +2140,14 @@ DriveFileSystemMetadata DriveFileSystem::GetMetadata() const {
   return metadata;
 }
 
-void DriveFileSystem::Observe(int type,
-                              const content::NotificationSource& source,
-                              const content::NotificationDetails& details) {
+void DriveFileSystem::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(pref_name == prefs::kDisableDriveHostedFiles);
 
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    PrefService* pref_service = profile_->GetPrefs();
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    if (*pref_name == prefs::kDisableDriveHostedFiles) {
-      SetHideHostedDocuments(
-          pref_service->GetBoolean(prefs::kDisableDriveHostedFiles));
-    }
-  } else {
-    NOTREACHED();
-  }
+  PrefService* pref_service = profile_->GetPrefs();
+  SetHideHostedDocuments(
+      pref_service->GetBoolean(prefs::kDisableDriveHostedFiles));
 }
 
 void DriveFileSystem::SetHideHostedDocuments(bool hide) {
diff --git a/chrome/browser/chromeos/drive/drive_file_system.h b/chrome/browser/chromeos/drive/drive_file_system.h
index 98de02b..c8f05eb 100644
--- a/chrome/browser/chromeos/drive/drive_file_system.h
+++ b/chrome/browser/chromeos/drive/drive_file_system.h
@@ -11,6 +11,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/timer.h"
 #include "chrome/browser/chromeos/drive/drive_cache.h"
 #include "chrome/browser/chromeos/drive/drive_feed_loader_observer.h"
@@ -18,7 +19,6 @@
 #include "chrome/browser/chromeos/drive/file_system/drive_operations.h"
 #include "chrome/browser/chromeos/drive/file_system/operation_observer.h"
 #include "chrome/browser/google_apis/gdata_errorcode.h"
-#include "content/public/browser/notification_observer.h"
 
 class PrefChangeRegistrar;
 
@@ -53,7 +53,7 @@ class RemoveOperation;
 class DriveFileSystem : public DriveFileSystemInterface,
                         public DriveFeedLoaderObserver,
                         public file_system::OperationObserver,
-                        public content::NotificationObserver {
+                        public PrefObserver {
  public:
   DriveFileSystem(Profile* profile,
                   DriveCache* cache,
@@ -143,10 +143,9 @@ class DriveFileSystem : public DriveFileSystemInterface,
   virtual DriveFileSystemMetadata GetMetadata() const OVERRIDE;
   virtual void Reload() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // file_system::OperationObserver overrides.
   virtual void OnDirectoryChangedByOperation(
diff --git a/chrome/browser/chromeos/drive/drive_sync_client.cc b/chrome/browser/chromeos/drive/drive_sync_client.cc
index 04d43cd..6de15df 100644
--- a/chrome/browser/chromeos/drive/drive_sync_client.cc
+++ b/chrome/browser/chromeos/drive/drive_sync_client.cc
@@ -430,9 +430,8 @@ void DriveSyncClient::OnUploadFileComplete(const std::string& resource_id,
   DoSyncLoop();
 }
 
-void DriveSyncClient::Observe(int type,
-                              const content::NotificationSource& source,
-                              const content::NotificationDetails& details) {
+void DriveSyncClient::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   // Resume the sync loop if gdata preferences are changed. Note that we
diff --git a/chrome/browser/chromeos/drive/drive_sync_client.h b/chrome/browser/chromeos/drive/drive_sync_client.h
index f0694e1..410b50e 100644
--- a/chrome/browser/chromeos/drive/drive_sync_client.h
+++ b/chrome/browser/chromeos/drive/drive_sync_client.h
@@ -11,12 +11,12 @@
 
 #include "base/callback_forward.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/time.h"
 #include "chrome/browser/chromeos/drive/drive_cache.h"
 #include "chrome/browser/chromeos/drive/drive_cache_observer.h"
 #include "chrome/browser/chromeos/drive/drive_file_system_observer.h"
 #include "chrome/browser/chromeos/drive/drive_resource_metadata.h"
-#include "content/public/browser/notification_observer.h"
 #include "net/base/network_change_notifier.h"
 
 class Profile;
@@ -45,7 +45,7 @@ class DriveSyncClientObserver;
 class DriveSyncClient
     : public DriveFileSystemObserver,
       public DriveCacheObserver,
-      public content::NotificationObserver,
+      public PrefObserver,
       public net::NetworkChangeNotifier::ConnectionTypeObserver {
  public:
   // Types of sync tasks.
@@ -178,10 +178,9 @@ class DriveSyncClient
   void OnUploadFileComplete(const std::string& resource_id,
                             DriveFileError error);
 
-  // content::NotificationObserver override.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver override.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // net::NetworkChangeNotifier::ConnectionTypeObserver override.
   virtual void OnConnectionTypeChanged(
diff --git a/chrome/browser/chromeos/extensions/file_browser_event_router.cc b/chrome/browser/chromeos/extensions/file_browser_event_router.cc
index 430e6f4..c4304333 100644
--- a/chrome/browser/chromeos/extensions/file_browser_event_router.cc
+++ b/chrome/browser/chromeos/extensions/file_browser_event_router.cc
@@ -385,41 +385,37 @@ void FileBrowserEventRouter::OnNetworkManagerChanged(
           scoped_ptr<ListValue>(new ListValue()), NULL, GURL());
 }
 
-void FileBrowserEventRouter::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void FileBrowserEventRouter::OnPreferenceChanged(PrefServiceBase* service,
+                                                 const std::string& pref_name) {
   if (!profile_ ||
       !extensions::ExtensionSystem::Get(profile_)->event_router()) {
     NOTREACHED();
     return;
   }
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    // If the policy just got disabled we have to unmount every device currently
-    // mounted. The opposite is fine - we can let the user re-plug her device to
-    // make it available.
-    if (*pref_name == prefs::kExternalStorageDisabled &&
-        profile_->GetPrefs()->GetBoolean(prefs::kExternalStorageDisabled)) {
-      DiskMountManager* manager = DiskMountManager::GetInstance();
-      DiskMountManager::MountPointMap mounts(manager->mount_points());
-      for (DiskMountManager::MountPointMap::const_iterator it = mounts.begin();
-           it != mounts.end(); ++it) {
-        LOG(INFO) << "Unmounting " << it->second.mount_path
-                  << " because of policy.";
-        manager->UnmountPath(it->second.mount_path,
-                             chromeos::UNMOUNT_OPTIONS_NONE);
-      }
-      return;
-    } else if (*pref_name == prefs::kDisableDriveOverCellular ||
-        *pref_name == prefs::kDisableDriveHostedFiles ||
-        *pref_name == prefs::kDisableDrive ||
-        *pref_name == prefs::kUse24HourClock) {
-      extensions::ExtensionSystem::Get(profile_)->event_router()->
-          DispatchEventToRenderers(
-              extensions::event_names::kOnFileBrowserPreferencesChanged,
-              scoped_ptr<ListValue>(new ListValue()), NULL, GURL());
+
+  // If the policy just got disabled we have to unmount every device currently
+  // mounted. The opposite is fine - we can let the user re-plug her device to
+  // make it available.
+  if (pref_name == prefs::kExternalStorageDisabled &&
+      profile_->GetPrefs()->GetBoolean(prefs::kExternalStorageDisabled)) {
+    DiskMountManager* manager = DiskMountManager::GetInstance();
+    DiskMountManager::MountPointMap mounts(manager->mount_points());
+    for (DiskMountManager::MountPointMap::const_iterator it = mounts.begin();
+         it != mounts.end(); ++it) {
+      LOG(INFO) << "Unmounting " << it->second.mount_path
+                << " because of policy.";
+      manager->UnmountPath(it->second.mount_path,
+                           chromeos::UNMOUNT_OPTIONS_NONE);
     }
+    return;
+  } else if (pref_name == prefs::kDisableDriveOverCellular ||
+             pref_name == prefs::kDisableDriveHostedFiles ||
+             pref_name == prefs::kDisableDrive ||
+             pref_name == prefs::kUse24HourClock) {
+    extensions::ExtensionSystem::Get(profile_)->event_router()->
+        DispatchEventToRenderers(
+            extensions::event_names::kOnFileBrowserPreferencesChanged,
+            scoped_ptr<ListValue>(new ListValue()), NULL, GURL());
   }
 }
 
diff --git a/chrome/browser/chromeos/extensions/file_browser_event_router.h b/chrome/browser/chromeos/extensions/file_browser_event_router.h
index 0313434..e2d926b 100644
--- a/chrome/browser/chromeos/extensions/file_browser_event_router.h
+++ b/chrome/browser/chromeos/extensions/file_browser_event_router.h
@@ -12,6 +12,7 @@
 #include "base/files/file_path_watcher.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string16.h"
 #include "base/synchronization/lock.h"
 #include "chrome/browser/chromeos/cros/network_library.h"
@@ -22,9 +23,6 @@
 #include "chrome/browser/profiles/refcounted_profile_keyed_service.h"
 #include "chrome/browser/profiles/refcounted_profile_keyed_service_factory.h"
 #include "chromeos/disks/disk_mount_manager.h"
-#include "content/public/browser/notification_details.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_source.h"
 
 class FileBrowserNotifications;
 class PrefChangeRegistrar;
@@ -41,7 +39,7 @@ class FileBrowserEventRouter
     : public RefcountedProfileKeyedService,
       public chromeos::disks::DiskMountManager::Observer,
       public chromeos::NetworkLibrary::NetworkManagerObserver,
-      public content::NotificationObserver,
+      public PrefObserver,
       public drive::DriveFileSystemObserver,
       public google_apis::DriveServiceObserver {
  public:
@@ -79,10 +77,9 @@ class FileBrowserEventRouter
   virtual void OnNetworkManagerChanged(
       chromeos::NetworkLibrary* network_library) OVERRIDE;
 
-  // Overridden from content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // Overridden from PrefObserver.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // drive::DriveServiceObserver overrides.
   virtual void OnProgressUpdate(
diff --git a/chrome/browser/chromeos/input_method/browser_state_monitor.cc b/chrome/browser/chromeos/input_method/browser_state_monitor.cc
index 3de50d3..0b2a8a2 100644
--- a/chrome/browser/chromeos/input_method/browser_state_monitor.cc
+++ b/chrome/browser/chromeos/input_method/browser_state_monitor.cc
@@ -153,9 +153,6 @@ void BrowserStateMonitor::Observe(
                InputMethodManager::STATE_BROWSER_SCREEN);
       break;
     }
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      break;  // just ignore the notification.
-    }
     default: {
       NOTREACHED();
       break;
diff --git a/chrome/browser/chromeos/input_method/browser_state_monitor_unittest.cc b/chrome/browser/chromeos/input_method/browser_state_monitor_unittest.cc
index 3746b80..b73b05a 100644
--- a/chrome/browser/chromeos/input_method/browser_state_monitor_unittest.cc
+++ b/chrome/browser/chromeos/input_method/browser_state_monitor_unittest.cc
@@ -237,22 +237,6 @@ TEST(BrowserStateMonitorTest, TestObserveAppTerminating) {
   EXPECT_EQ(0, monitor.update_user_pref_count());
 }
 
-TEST(BrowserStateMonitorTest, TestObservePrefChanged) {
-  TestingPrefService prefs;
-  RegisterTestPrefs(&prefs);
-  MockInputMethodManager mock_manager;
-  TestableBrowserStateMonitor monitor(&mock_manager);
-  monitor.SetPrefServiceForTesting(&prefs);
-
-  EXPECT_EQ(1, mock_manager.set_state_count_);
-  monitor.Observe(chrome::NOTIFICATION_PREF_CHANGED,
-                  content::NotificationService::AllSources(),
-                  content::NotificationService::NoDetails());
-
-  // NOTIFICATION_PREF_CHANGED should be ignored.
-  EXPECT_EQ(1, mock_manager.set_state_count_);
-}
-
 TEST(BrowserStateMonitorTest, TestUpdatePrefOnLoginScreen) {
   TestingPrefService prefs;
   RegisterTestPrefs(&prefs);
diff --git a/chrome/browser/chromeos/preferences.cc b/chrome/browser/chromeos/preferences.cc
index 793c7f9..091369f 100644
--- a/chrome/browser/chromeos/preferences.cc
+++ b/chrome/browser/chromeos/preferences.cc
@@ -30,8 +30,6 @@
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
-#include "content/public/browser/notification_details.h"
-#include "content/public/browser/notification_source.h"
 #include "googleurl/src/gurl.h"
 #include "ui/base/events/event_constants.h"
 #include "unicode/timezone.h"
@@ -393,11 +391,9 @@ void Preferences::SetInputMethodListForTesting() {
   SetInputMethodList();
 }
 
-void Preferences::Observe(int type,
-                          const content::NotificationSource& source,
-                          const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED)
-    NotifyPrefChanged(content::Details<std::string>(details).ptr());
+void Preferences::OnPreferenceChanged(PrefServiceBase* service,
+                                      const std::string& pref_name) {
+  NotifyPrefChanged(&pref_name);
 }
 
 void Preferences::NotifyPrefChanged(const std::string* pref_name) {
diff --git a/chrome/browser/chromeos/preferences.h b/chrome/browser/chromeos/preferences.h
index d14acfc..4c27fd3 100644
--- a/chrome/browser/chromeos/preferences.h
+++ b/chrome/browser/chromeos/preferences.h
@@ -9,9 +9,9 @@
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/chromeos/language_preferences.h"
-#include "content/public/browser/notification_observer.h"
 
 class PrefService;
 
@@ -24,7 +24,7 @@ class InputMethodManager;
 // is first initialized, it will initialize the OS settings to what's stored in
 // the preferences. These include touchpad settings, etc.
 // When the preferences change, we change the settings to reflect the new value.
-class Preferences : public content::NotificationObserver {
+class Preferences : public PrefObserver {
  public:
   Preferences();
   explicit Preferences(
@@ -37,10 +37,9 @@ class Preferences : public content::NotificationObserver {
   // This method will initialize Chrome OS settings to values in user prefs.
   void Init(PrefService* prefs);
 
-  // Overridden from content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   void InitUserPrefsForTesting(PrefService* prefs);
   void SetInputMethodListForTesting();
diff --git a/chrome/browser/chromeos/proxy_config_service_impl.cc b/chrome/browser/chromeos/proxy_config_service_impl.cc
index 3b20231..5eca442 100644
--- a/chrome/browser/chromeos/proxy_config_service_impl.cc
+++ b/chrome/browser/chromeos/proxy_config_service_impl.cc
@@ -586,29 +586,26 @@ void ProxyConfigServiceImpl::RegisterPrefs(PrefService* pref_service) {
 
 //------------------ ProxyConfigServiceImpl: private methods -------------------
 
-void ProxyConfigServiceImpl::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED &&
-      *(content::Details<std::string>(details).ptr()) ==
-          prefs::kUseSharedProxies) {
-    if (content::Source<PrefService>(source).ptr() == prefs()) {
-      VLOG(1) << "New use-shared-proxies = " << GetUseSharedProxies();
-      // Determine new proxy config which may have changed because of new
-      // use-shared-proxies. If necessary, activate it.
-      Network* network = NULL;
-      if (!active_network_.empty()) {
-        network = CrosLibrary::Get()->GetNetworkLibrary()->FindNetworkByPath(
-            active_network_);
-        if (!network)
-          LOG(WARNING) << "Can't find requested network " << active_network_;
-      }
-      DetermineEffectiveConfig(network, true);
+void ProxyConfigServiceImpl::OnPreferenceChanged(PrefServiceBase* service,
+                                                 const std::string& pref_name) {
+  DCHECK(service == prefs());
+  VLOG(1) << "New use-shared-proxies = " << GetUseSharedProxies();
+
+  if (pref_name == prefs::kUseSharedProxies) {
+    // Determine new proxy config which may have changed because of new
+    // use-shared-proxies. If necessary, activate it.
+    Network* network = NULL;
+    if (!active_network_.empty()) {
+      network = CrosLibrary::Get()->GetNetworkLibrary()->FindNetworkByPath(
+          active_network_);
+      if (!network)
+        LOG(WARNING) << "Can't find requested network " << active_network_;
     }
+    DetermineEffectiveConfig(network, true);
     return;
   }
-  PrefProxyConfigTrackerImpl::Observe(type, source, details);
+
+  PrefProxyConfigTrackerImpl::OnPreferenceChanged(service, pref_name);
 }
 
 void ProxyConfigServiceImpl::OnUISetProxyConfig() {
diff --git a/chrome/browser/chromeos/proxy_config_service_impl.h b/chrome/browser/chromeos/proxy_config_service_impl.h
index 92df0d0..78026ba 100644
--- a/chrome/browser/chromeos/proxy_config_service_impl.h
+++ b/chrome/browser/chromeos/proxy_config_service_impl.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/values.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/chromeos/cros/network_library.h"
@@ -213,10 +214,9 @@ class ProxyConfigServiceImpl
 #endif  // defined(UNIT_TEST)
 
  private:
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Called from the various UISetProxyConfigTo*.
   void OnUISetProxyConfig();
diff --git a/chrome/browser/chromeos/system/ash_system_tray_delegate.cc b/chrome/browser/chromeos/system/ash_system_tray_delegate.cc
index a62883e8..cc6930c 100644
--- a/chrome/browser/chromeos/system/ash_system_tray_delegate.cc
+++ b/chrome/browser/chromeos/system/ash_system_tray_delegate.cc
@@ -26,6 +26,7 @@
 #include "base/chromeos/chromeos_version.h"
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chromeos/accessibility/accessibility_util.h"
@@ -151,6 +152,7 @@ class SystemTrayDelegate : public ash::SystemTrayDelegate,
                            public NetworkLibrary::NetworkManagerObserver,
                            public NetworkLibrary::NetworkObserver,
                            public NetworkLibrary::CellularDataPlanObserver,
+                           public PrefObserver,
                            public google_apis::DriveServiceObserver,
                            public content::NotificationObserver,
                            public input_method::InputMethodManager::Observer,
@@ -1088,26 +1090,6 @@ class SystemTrayDelegate : public ash::SystemTrayDelegate,
         ObserveGDataUpdates();
         break;
       }
-      case chrome::NOTIFICATION_PREF_CHANGED: {
-        std::string pref = *content::Details<std::string>(details).ptr();
-        PrefService* service = content::Source<PrefService>(source).ptr();
-        if (pref == prefs::kUse24HourClock) {
-          UpdateClockType(service);
-        } else if (pref == prefs::kLanguageRemapSearchKeyTo) {
-          search_key_mapped_to_ =
-              service->GetInteger(prefs::kLanguageRemapSearchKeyTo);
-        } else if (pref == prefs::kSpokenFeedbackEnabled) {
-          ash::AccessibilityObserver* observer =
-              tray_->accessibility_observer();
-          if (observer) {
-            observer->OnAccessibilityModeChanged(
-                service->GetBoolean(prefs::kSpokenFeedbackEnabled));
-          }
-        } else {
-          NOTREACHED();
-        }
-        break;
-      }
       case chrome::NOTIFICATION_PROFILE_CREATED: {
         SetProfile(content::Source<Profile>(source).ptr());
         registrar_.Remove(this,
@@ -1126,6 +1108,25 @@ class SystemTrayDelegate : public ash::SystemTrayDelegate,
     }
   }
 
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref) OVERRIDE {
+    if (pref == prefs::kUse24HourClock) {
+      UpdateClockType(static_cast<PrefService*>(service));
+    } else if (pref == prefs::kLanguageRemapSearchKeyTo) {
+      search_key_mapped_to_ =
+          service->GetInteger(prefs::kLanguageRemapSearchKeyTo);
+    } else if (pref == prefs::kSpokenFeedbackEnabled) {
+      ash::AccessibilityObserver* observer =
+          tray_->accessibility_observer();
+      if (observer) {
+        observer->OnAccessibilityModeChanged(
+            service->GetBoolean(prefs::kSpokenFeedbackEnabled));
+      }
+    } else {
+      NOTREACHED();
+    }
+  }
+
   // Overridden from InputMethodManager::Observer.
   virtual void InputMethodChanged(
       input_method::InputMethodManager* manager, bool show_message) OVERRIDE {
diff --git a/chrome/browser/content_settings/content_settings_default_provider.cc b/chrome/browser/content_settings/content_settings_default_provider.cc
index 97e6b55..ca56f7a 100644
--- a/chrome/browser/content_settings/content_settings_default_provider.cc
+++ b/chrome/browser/content_settings/content_settings_default_provider.cc
@@ -276,17 +276,13 @@ void DefaultProvider::ShutdownOnUIThread() {
   prefs_ = NULL;
 }
 
-void DefaultProvider::Observe(int type,
-                              const content::NotificationSource& source,
-                              const content::NotificationDetails& details) {
+void DefaultProvider::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(content::Source<PrefService>(source).ptr(), prefs_);
-
+  DCHECK_EQ(prefs_, service);
   if (updating_preferences_)
     return;
 
-  const std::string& name = *content::Details<std::string>(details).ptr();
   if (name == prefs::kDefaultContentSettings) {
     ReadDefaultSettings(true);
   } else if (name == prefs::kGeolocationDefaultContentSetting) {
diff --git a/chrome/browser/content_settings/content_settings_default_provider.h b/chrome/browser/content_settings/content_settings_default_provider.h
index 2e5d96a..9235293 100644
--- a/chrome/browser/content_settings/content_settings_default_provider.h
+++ b/chrome/browser/content_settings/content_settings_default_provider.h
@@ -12,10 +12,9 @@
 #include "base/basictypes.h"
 #include "base/memory/linked_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/synchronization/lock.h"
 #include "chrome/browser/content_settings/content_settings_observable_provider.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
 
 class PrefService;
 
@@ -25,7 +24,7 @@ namespace content_settings {
 // user prefs. If no default values are set by the user we use the hard coded
 // default values.
 class DefaultProvider : public ObservableProvider,
-                        public content::NotificationObserver {
+                        public PrefObserver {
  public:
   static void RegisterUserPrefs(PrefService* prefs);
 
@@ -51,10 +50,9 @@ class DefaultProvider : public ObservableProvider,
 
   virtual void ShutdownOnUIThread() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   // Sets the fields of |settings| based on the values in |dictionary|.
diff --git a/chrome/browser/content_settings/content_settings_policy_provider.cc b/chrome/browser/content_settings/content_settings_policy_provider.cc
index cb24bfd..0160b51 100644
--- a/chrome/browser/content_settings/content_settings_policy_provider.cc
+++ b/chrome/browser/content_settings/content_settings_policy_provider.cc
@@ -422,14 +422,11 @@ void PolicyProvider::ShutdownOnUIThread() {
   prefs_ = NULL;
 }
 
-void PolicyProvider::Observe(int type,
-                             const content::NotificationSource& source,
-                             const content::NotificationDetails& details) {
+void PolicyProvider::OnPreferenceChanged(PrefServiceBase* service,
+                                         const std::string& name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(content::Source<PrefService>(source).ptr(), prefs_);
+  DCHECK_EQ(prefs_, service);
 
-  const std::string& name = *content::Details<std::string>(details).ptr();
   if (name == prefs::kManagedDefaultCookiesSetting) {
     UpdateManagedDefaultSetting(CONTENT_SETTINGS_TYPE_COOKIES);
   } else if (name == prefs::kManagedDefaultImagesSetting) {
@@ -462,10 +459,8 @@ void PolicyProvider::Observe(int type,
              name == prefs::kManagedNotificationsBlockedForUrls) {
     ReadManagedContentSettings(true);
     ReadManagedDefaultSettings();
-  } else {
-    NOTREACHED();
-    return;
   }
+
   NotifyObservers(ContentSettingsPattern(),
                   ContentSettingsPattern(),
                   CONTENT_SETTINGS_TYPE_DEFAULT,
diff --git a/chrome/browser/content_settings/content_settings_policy_provider.h b/chrome/browser/content_settings/content_settings_policy_provider.h
index 586a4d40..096c09b 100644
--- a/chrome/browser/content_settings/content_settings_policy_provider.h
+++ b/chrome/browser/content_settings/content_settings_policy_provider.h
@@ -11,10 +11,10 @@
 
 #include "base/basictypes.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/synchronization/lock.h"
 #include "chrome/browser/content_settings/content_settings_observable_provider.h"
 #include "chrome/browser/content_settings/content_settings_origin_identifier_value_map.h"
-#include "content/public/browser/notification_observer.h"
 
 class PrefService;
 
@@ -22,7 +22,7 @@ namespace content_settings {
 
 // PolicyProvider that provides managed content-settings.
 class PolicyProvider : public ObservableProvider,
-                       public content::NotificationObserver {
+                       public PrefObserver {
  public:
   explicit PolicyProvider(PrefService* prefs);
   virtual ~PolicyProvider();
@@ -46,10 +46,10 @@ class PolicyProvider : public ObservableProvider,
 
   virtual void ShutdownOnUIThread() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
  private:
   // Reads the policy managed default settings.
   void ReadManagedDefaultSettings();
diff --git a/chrome/browser/content_settings/content_settings_pref_provider.cc b/chrome/browser/content_settings/content_settings_pref_provider.cc
index 8b4887e..e5ad337 100644
--- a/chrome/browser/content_settings/content_settings_pref_provider.cc
+++ b/chrome/browser/content_settings/content_settings_pref_provider.cc
@@ -217,15 +217,11 @@ void PrefProvider::ClearAllContentSettingsRules(
                   std::string());
 }
 
-void PrefProvider::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void PrefProvider::OnPreferenceChanged(PrefServiceBase* service,
+                                       const std::string& name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(content::Source<PrefService>(source).ptr(), prefs_);
-  DCHECK_EQ(std::string(prefs::kContentSettingsPatternPairs),
-            *content::Details<std::string>(details).ptr());
+  DCHECK_EQ(prefs_, service);
+  DCHECK_EQ(std::string(prefs::kContentSettingsPatternPairs), name);
 
   if (updating_preferences_)
     return;
diff --git a/chrome/browser/content_settings/content_settings_pref_provider.h b/chrome/browser/content_settings/content_settings_pref_provider.h
index 9595de7..1efc5ccb 100644
--- a/chrome/browser/content_settings/content_settings_pref_provider.h
+++ b/chrome/browser/content_settings/content_settings_pref_provider.h
@@ -11,12 +11,11 @@
 
 #include "base/basictypes.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/synchronization/lock.h"
 #include "chrome/browser/content_settings/content_settings_observable_provider.h"
 #include "chrome/browser/content_settings/content_settings_origin_identifier_value_map.h"
 #include "chrome/browser/content_settings/content_settings_utils.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
 
 class PrefService;
 
@@ -29,7 +28,7 @@ namespace content_settings {
 // Content settings provider that provides content settings from the user
 // preference.
 class PrefProvider : public ObservableProvider,
-                     public content::NotificationObserver {
+                     public PrefObserver {
  public:
   static void RegisterUserPrefs(PrefService* prefs);
 
@@ -55,10 +54,9 @@ class PrefProvider : public ObservableProvider,
 
   virtual void ShutdownOnUIThread() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   friend class DeadlockCheckerThread;  // For testing.
diff --git a/chrome/browser/content_settings/content_settings_pref_provider_unittest.cc b/chrome/browser/content_settings/content_settings_pref_provider_unittest.cc
index 3d9de68..c61b4a5 100644
--- a/chrome/browser/content_settings/content_settings_pref_provider_unittest.cc
+++ b/chrome/browser/content_settings/content_settings_pref_provider_unittest.cc
@@ -11,6 +11,7 @@
 #include "base/prefs/default_pref_store.h"
 #include "base/prefs/overlay_user_pref_store.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/prefs/testing_pref_store.h"
 #include "base/threading/platform_thread.h"
 #include "base/values.h"
@@ -20,13 +21,11 @@
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/prefs/pref_service_mock_builder.h"
 #include "chrome/browser/prefs/scoped_user_pref_update.h"
-#include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/testing_pref_service.h"
 #include "chrome/test/base/testing_profile.h"
-#include "content/public/browser/notification_observer.h"
 #include "content/public/test/test_browser_thread.h"
 #include "googleurl/src/gurl.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -54,7 +53,7 @@ class DeadlockCheckerThread : public base::PlatformThread::Delegate {
 
 // A helper for observing an preference changes and testing whether
 // |PrefProvider| holds a lock when the preferences change.
-class DeadlockCheckerObserver : public content::NotificationObserver {
+class DeadlockCheckerObserver : public PrefObserver {
  public:
   // |DeadlockCheckerObserver| doesn't take the ownership of |prefs| or
   // ||provider|.
@@ -66,12 +65,10 @@ class DeadlockCheckerObserver : public content::NotificationObserver {
   }
   virtual ~DeadlockCheckerObserver() {}
 
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) {
-    ASSERT_EQ(type, chrome::NOTIFICATION_PREF_CHANGED);
-    // Check whether |provider_| holds its lock. For this, we need a separate
-    // thread.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) {
+    // Check whether |provider_| holds its lock. For this, we need a
+    // separate thread.
     DeadlockCheckerThread thread(provider_);
     base::PlatformThreadHandle handle = base::kNullThreadHandle;
     ASSERT_TRUE(base::PlatformThread::Create(0, &thread, &handle));
diff --git a/chrome/browser/content_settings/cookie_settings.cc b/chrome/browser/content_settings/cookie_settings.cc
index 9407cbc..aed029e 100644
--- a/chrome/browser/content_settings/cookie_settings.cc
+++ b/chrome/browser/content_settings/cookie_settings.cc
@@ -155,20 +155,14 @@ void CookieSettings::ResetCookieSetting(
       CONTENT_SETTING_DEFAULT);
 }
 
-void CookieSettings::Observe(int type,
-                             const content::NotificationSource& source,
-                             const content::NotificationDetails& details) {
+void CookieSettings::OnPreferenceChanged(PrefServiceBase* prefs,
+                                         const std::string& name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(std::string(prefs::kBlockThirdPartyCookies),
-            *content::Details<std::string>(details).ptr());
-
-  PrefService* prefs = content::Source<PrefService>(source).ptr();
-  {
-    base::AutoLock auto_lock(lock_);
-    block_third_party_cookies_ = prefs->GetBoolean(
-        prefs::kBlockThirdPartyCookies);
-  }
+  DCHECK_EQ(std::string(prefs::kBlockThirdPartyCookies), name);
+
+  base::AutoLock auto_lock(lock_);
+  block_third_party_cookies_ = prefs->GetBoolean(
+      prefs::kBlockThirdPartyCookies);
 }
 
 void CookieSettings::ShutdownOnUIThread() {
diff --git a/chrome/browser/content_settings/cookie_settings.h b/chrome/browser/content_settings/cookie_settings.h
index f1aba03..853f1df 100644
--- a/chrome/browser/content_settings/cookie_settings.h
+++ b/chrome/browser/content_settings/cookie_settings.h
@@ -11,12 +11,12 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/singleton.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/synchronization/lock.h"
 #include "chrome/browser/content_settings/host_content_settings_map.h"
 #include "chrome/browser/profiles/refcounted_profile_keyed_service.h"
 #include "chrome/browser/profiles/refcounted_profile_keyed_service_factory.h"
 #include "chrome/common/content_settings.h"
-#include "content/public/browser/notification_observer.h"
 
 class ContentSettingsPattern;
 class CookieSettingsWrapper;
@@ -29,7 +29,7 @@ class Profile;
 // thread and read on any thread. One instance per profile.
 
 class CookieSettings
-    : public content::NotificationObserver,
+    : public PrefObserver,
       public RefcountedProfileKeyedService {
  public:
   CookieSettings(
@@ -91,10 +91,9 @@ class CookieSettings
   void ResetCookieSetting(const ContentSettingsPattern& primary_pattern,
                           const ContentSettingsPattern& secondary_pattern);
 
-  // |NotificationObserver| implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // |PrefObserver| implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Detaches the |CookieSettings| from all |Profile|-related objects like
   // |PrefService|. This methods needs to be called before destroying the
diff --git a/chrome/browser/extensions/api/font_settings/font_settings_api.cc b/chrome/browser/extensions/api/font_settings/font_settings_api.cc
index 88a1149..053e417 100644
--- a/chrome/browser/extensions/api/font_settings/font_settings_api.cc
+++ b/chrome/browser/extensions/api/font_settings/font_settings_api.cc
@@ -87,7 +87,7 @@ std::string MaybeGetLocalizedFontName(const std::string& font_name) {
 // Registers |obs| to observe per-script font prefs under the path |map_name|.
 void RegisterFontFamilyMapObserver(PrefChangeRegistrar* registrar,
                                    const char* map_name,
-                                   content::NotificationObserver* obs) {
+                                   PrefObserver* obs) {
   for (size_t i = 0; i < prefs::kWebKitScriptsForFontFamilyMapsLength; ++i) {
     const char* script = prefs::kWebKitScriptsForFontFamilyMaps[i];
     std::string pref_name = base::StringPrintf("%s.%s", map_name, script);
@@ -132,24 +132,18 @@ void FontSettingsEventRouter::Init() {
 }
 
 void FontSettingsEventRouter::AddPrefToObserve(const char* pref_name,
-                                                        const char* event_name,
-                                                        const char* key) {
+                                               const char* event_name,
+                                               const char* key) {
   registrar_.Add(pref_name, this);
   pref_event_map_[pref_name] = std::make_pair(event_name, key);
 }
 
-void FontSettingsEventRouter::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-
-  PrefService* pref_service = content::Source<PrefService>(source).ptr();
+void FontSettingsEventRouter::OnPreferenceChanged(
+    PrefServiceBase* pref_service,
+    const std::string& pref_name) {
   bool incognito = (pref_service != profile_->GetPrefs());
   // We're only observing pref changes on the regular profile.
   DCHECK(!incognito);
-  const std::string& pref_name =
-      *content::Details<const std::string>(details).ptr();
 
   PrefEventMap::iterator iter = pref_event_map_.find(pref_name);
   if (iter != pref_event_map_.end()) {
@@ -172,12 +166,12 @@ void FontSettingsEventRouter::Observe(
 }
 
 void FontSettingsEventRouter::OnFontNamePrefChanged(
-    PrefService* pref_service,
+    PrefServiceBase* pref_service,
     const std::string& pref_name,
     const std::string& generic_family,
     const std::string& script,
     bool incognito) {
-  const PrefService::Preference* pref = pref_service->FindPreference(
+  const PrefServiceBase::Preference* pref = pref_service->FindPreference(
       pref_name.c_str());
   CHECK(pref);
 
@@ -205,12 +199,12 @@ void FontSettingsEventRouter::OnFontNamePrefChanged(
 }
 
 void FontSettingsEventRouter::OnFontPrefChanged(
-    PrefService* pref_service,
+    PrefServiceBase* pref_service,
     const std::string& pref_name,
     const std::string& event_name,
     const std::string& key,
     bool incognito) {
-  const PrefService::Preference* pref = pref_service->FindPreference(
+  const PrefServiceBase::Preference* pref = pref_service->FindPreference(
       pref_name.c_str());
   CHECK(pref);
 
diff --git a/chrome/browser/extensions/api/font_settings/font_settings_api.h b/chrome/browser/extensions/api/font_settings/font_settings_api.h
index 9c73cf0..266b962 100644
--- a/chrome/browser/extensions/api/font_settings/font_settings_api.h
+++ b/chrome/browser/extensions/api/font_settings/font_settings_api.h
@@ -13,6 +13,7 @@
 #include <utility>
 
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/extensions/extension_function.h"
 #include "chrome/browser/prefs/pref_service.h"
 
@@ -20,7 +21,7 @@ namespace extensions {
 
 // This class observes pref changed events on a profile and dispatches the
 // corresponding extension API events to extensions.
-class FontSettingsEventRouter : public content::NotificationObserver {
+class FontSettingsEventRouter : public PrefObserver {
  public:
   // Constructor for observing pref changed events on |profile|. Stores a
   // pointer to |profile| but does not take ownership. |profile| must be
@@ -48,17 +49,16 @@ class FontSettingsEventRouter : public content::NotificationObserver {
                         const char* event_name,
                         const char* key);
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Dispatches a changed event for the font setting for |generic_family| and
   // |script| to extensions. The new value of the setting is the value of
   // browser pref |pref_name|. If the pref changed on the incognito profile,
   // |incognito| must be set to true for extensions to get the appropriate
   // event.
-  void OnFontNamePrefChanged(PrefService* pref_service,
+  void OnFontNamePrefChanged(PrefServiceBase* pref_service,
                              const std::string& pref_name,
                              const std::string& generic_family,
                              const std::string& script,
@@ -70,7 +70,7 @@ class FontSettingsEventRouter : public content::NotificationObserver {
   // under the key |key|. If the pref changed on the incognito profile,
   // |incognito| must be set to true for extensions to get the appropriate
   // event.
-  void OnFontPrefChanged(PrefService* pref_service,
+  void OnFontPrefChanged(PrefServiceBase* pref_service,
                          const std::string& pref_name,
                          const std::string& event_name,
                          const std::string& key,
diff --git a/chrome/browser/extensions/api/managed_mode/managed_mode_api.cc b/chrome/browser/extensions/api/managed_mode/managed_mode_api.cc
index 82be3b6..2be512c 100644
--- a/chrome/browser/extensions/api/managed_mode/managed_mode_api.cc
+++ b/chrome/browser/extensions/api/managed_mode/managed_mode_api.cc
@@ -51,13 +51,9 @@ void ExtensionManagedModeEventRouter::Init() {
 ExtensionManagedModeEventRouter::~ExtensionManagedModeEventRouter() {
 }
 
-void ExtensionManagedModeEventRouter::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  const std::string& pref_name =
-      *content::Details<std::string>(details).ptr();
+void ExtensionManagedModeEventRouter::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
   DCHECK_EQ(std::string(prefs::kInManagedMode), pref_name);
 
   DictionaryValue* dict = new DictionaryValue();
diff --git a/chrome/browser/extensions/api/managed_mode/managed_mode_api.h b/chrome/browser/extensions/api/managed_mode/managed_mode_api.h
index 8c3245a..e85a75a 100644
--- a/chrome/browser/extensions/api/managed_mode/managed_mode_api.h
+++ b/chrome/browser/extensions/api/managed_mode/managed_mode_api.h
@@ -9,6 +9,7 @@
 #define CHROME_BROWSER_EXTENSIONS_API_MANAGED_MODE_MANAGED_MODE_API_H_
 
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/extensions/extension_function.h"
 #include "content/public/browser/notification_observer.h"
 
@@ -16,17 +17,16 @@ class Profile;
 
 namespace extensions {
 
-class ExtensionManagedModeEventRouter : public content::NotificationObserver {
+class ExtensionManagedModeEventRouter : public PrefObserver {
  public:
   explicit ExtensionManagedModeEventRouter(Profile* profile);
   virtual ~ExtensionManagedModeEventRouter();
 
   void Init();
 
-  // content::NotificationObserver implementation:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   PrefChangeRegistrar registrar_;
diff --git a/chrome/browser/extensions/api/preference/preference_api.cc b/chrome/browser/extensions/api/preference/preference_api.cc
index a555e36..46e6751 100644
--- a/chrome/browser/extensions/api/preference/preference_api.cc
+++ b/chrome/browser/extensions/api/preference/preference_api.cc
@@ -253,16 +253,12 @@ PreferenceEventRouter::PreferenceEventRouter(Profile* profile)
 
 PreferenceEventRouter::~PreferenceEventRouter() { }
 
-void PreferenceEventRouter::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  OnPrefChanged(content::Source<PrefService>(source).ptr(),
-                *content::Details<const std::string>(details).ptr());
+void PreferenceEventRouter::OnPreferenceChanged(PrefServiceBase* service,
+                                                const std::string& pref_name) {
+  OnPrefChanged(service, pref_name);
 }
 
-void PreferenceEventRouter::OnPrefChanged(PrefService* pref_service,
+void PreferenceEventRouter::OnPrefChanged(PrefServiceBase* pref_service,
                                           const std::string& browser_pref) {
   bool incognito = (pref_service != profile_->GetPrefs());
 
@@ -275,7 +271,7 @@ void PreferenceEventRouter::OnPrefChanged(PrefService* pref_service,
   ListValue args;
   DictionaryValue* dict = new DictionaryValue();
   args.Append(dict);
-  const PrefService::Preference* pref =
+  const PrefServiceBase::Preference* pref =
       pref_service->FindPreference(browser_pref.c_str());
   CHECK(pref);
   ExtensionService* extension_service = profile_->GetExtensionService();
diff --git a/chrome/browser/extensions/api/preference/preference_api.h b/chrome/browser/extensions/api/preference/preference_api.h
index 7bf67cd..c6e7f4b 100644
--- a/chrome/browser/extensions/api/preference/preference_api.h
+++ b/chrome/browser/extensions/api/preference/preference_api.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/extensions/extension_function.h"
 #include "content/public/browser/notification_observer.h"
 
@@ -19,18 +20,18 @@ class Value;
 
 namespace extensions {
 
-class PreferenceEventRouter : public content::NotificationObserver {
+class PreferenceEventRouter : public PrefObserver {
  public:
   explicit PreferenceEventRouter(Profile* profile);
   virtual ~PreferenceEventRouter();
 
  private:
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
-  void OnPrefChanged(PrefService* pref_service, const std::string& pref_key);
+  void OnPrefChanged(PrefServiceBase* pref_service,
+                     const std::string& pref_key);
 
   // This method dispatches events to the extension message service.
   void DispatchEvent(const std::string& extension_id,
diff --git a/chrome/browser/extensions/component_loader.cc b/chrome/browser/extensions/component_loader.cc
index e7e5b16..51f0acf 100644
--- a/chrome/browser/extensions/component_loader.cc
+++ b/chrome/browser/extensions/component_loader.cc
@@ -407,13 +407,9 @@ void ComponentLoader::AddDefaultComponentExtensions() {
   AddScriptBubble();
 }
 
-void ComponentLoader::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(std::string(prefs::kEnterpriseWebStoreURL),
-            *content::Details<const std::string>(details).ptr());
+void ComponentLoader::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
+  DCHECK_EQ(std::string(prefs::kEnterpriseWebStoreURL), pref_name);
   AddOrReloadEnterpriseWebStore();
 }
 
diff --git a/chrome/browser/extensions/component_loader.h b/chrome/browser/extensions/component_loader.h
index 8c68775..beb2e6b 100644
--- a/chrome/browser/extensions/component_loader.h
+++ b/chrome/browser/extensions/component_loader.h
@@ -11,8 +11,8 @@
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/values.h"
-#include "content/public/browser/notification_observer.h"
 
 class ExtensionServiceInterface;
 class PrefService;
@@ -22,7 +22,7 @@ namespace extensions {
 class Extension;
 
 // For registering, loading, and unloading component extensions.
-class ComponentLoader : public content::NotificationObserver {
+class ComponentLoader : public PrefObserver {
  public:
   ComponentLoader(ExtensionServiceInterface* extension_service,
                   PrefService* prefs,
@@ -69,10 +69,9 @@ class ComponentLoader : public content::NotificationObserver {
   // Adds the default component extensions.
   void AddDefaultComponentExtensions();
 
-  // content::NotificationObserver implementation
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   static void RegisterUserPrefs(PrefService* prefs);
 
diff --git a/chrome/browser/extensions/extension_prefs_unittest.cc b/chrome/browser/extensions/extension_prefs_unittest.cc
index 22a8c50..67eb2a1 100644
--- a/chrome/browser/extensions/extension_prefs_unittest.cc
+++ b/chrome/browser/extensions/extension_prefs_unittest.cc
@@ -15,6 +15,7 @@
 #include "chrome/browser/extensions/extension_pref_value_map.h"
 #include "chrome/browser/extensions/extension_prefs.h"
 #include "chrome/browser/prefs/scoped_user_pref_update.h"
+#include "chrome/browser/prefs/pref_observer_mock.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/extensions/extension_manifest_constants.h"
 #include "chrome/common/extensions/permissions/permission_set.h"
@@ -1052,60 +1053,60 @@ class ExtensionPrefsNotifyWhenNeeded : public ExtensionPrefsPrepopulatedTest {
     using testing::Mock;
     using testing::StrEq;
 
-    content::MockNotificationObserver observer;
+    PrefObserverMock observer;
     PrefChangeRegistrar registrar;
     registrar.Init(prefs()->pref_service());
     registrar.Add(kPref1, &observer);
 
-    content::MockNotificationObserver incognito_observer;
+    PrefObserverMock incognito_observer;
     scoped_ptr<PrefService> incog_prefs(prefs_.CreateIncognitoPrefService());
     PrefChangeRegistrar incognito_registrar;
     incognito_registrar.Init(incog_prefs.get());
     incognito_registrar.Add(kPref1, &incognito_observer);
 
     // Write value and check notification.
-    EXPECT_CALL(observer, Observe(_, _, _));
-    EXPECT_CALL(incognito_observer, Observe(_, _, _));
+    EXPECT_CALL(observer, OnPreferenceChanged(_, _));
+    EXPECT_CALL(incognito_observer, OnPreferenceChanged(_, _));
     InstallExtControlledPref(ext1_, kPref1,
         Value::CreateStringValue("https://www.chromium.org"));
     Mock::VerifyAndClearExpectations(&observer);
     Mock::VerifyAndClearExpectations(&incognito_observer);
 
     // Write same value.
-    EXPECT_CALL(observer, Observe(_, _, _)).Times(0);
-    EXPECT_CALL(incognito_observer, Observe(_, _, _)).Times(0);
+    EXPECT_CALL(observer, OnPreferenceChanged(_, _)).Times(0);
+    EXPECT_CALL(incognito_observer, OnPreferenceChanged(_, _)).Times(0);
     InstallExtControlledPref(ext1_, kPref1,
         Value::CreateStringValue("https://www.chromium.org"));
     Mock::VerifyAndClearExpectations(&observer);
     Mock::VerifyAndClearExpectations(&incognito_observer);
 
     // Change value.
-    EXPECT_CALL(observer, Observe(_, _, _));
-    EXPECT_CALL(incognito_observer, Observe(_, _, _));
+    EXPECT_CALL(observer, OnPreferenceChanged(_, _));
+    EXPECT_CALL(incognito_observer, OnPreferenceChanged(_, _));
     InstallExtControlledPref(ext1_, kPref1,
         Value::CreateStringValue("chrome://newtab"));
     Mock::VerifyAndClearExpectations(&observer);
     Mock::VerifyAndClearExpectations(&incognito_observer);
 
     // Change only incognito persistent value.
-    EXPECT_CALL(observer, Observe(_, _, _)).Times(0);
-    EXPECT_CALL(incognito_observer, Observe(_, _, _));
+    EXPECT_CALL(observer, OnPreferenceChanged(_, _)).Times(0);
+    EXPECT_CALL(incognito_observer, OnPreferenceChanged(_, _));
     InstallExtControlledPrefIncognito(ext1_, kPref1,
         Value::CreateStringValue("chrome://newtab2"));
     Mock::VerifyAndClearExpectations(&observer);
     Mock::VerifyAndClearExpectations(&incognito_observer);
 
     // Change only incognito session-only value.
-    EXPECT_CALL(observer, Observe(_, _, _)).Times(0);
-    EXPECT_CALL(incognito_observer, Observe(_, _, _));
+    EXPECT_CALL(observer, OnPreferenceChanged(_, _)).Times(0);
+    EXPECT_CALL(incognito_observer, OnPreferenceChanged(_, _));
     InstallExtControlledPrefIncognito(ext1_, kPref1,
         Value::CreateStringValue("chrome://newtab3"));
     Mock::VerifyAndClearExpectations(&observer);
     Mock::VerifyAndClearExpectations(&incognito_observer);
 
     // Uninstall.
-    EXPECT_CALL(observer, Observe(_, _, _));
-    EXPECT_CALL(incognito_observer, Observe(_, _, _));
+    EXPECT_CALL(observer, OnPreferenceChanged(_, _));
+    EXPECT_CALL(incognito_observer, OnPreferenceChanged(_, _));
     UninstallExtension(ext1_->id());
     Mock::VerifyAndClearExpectations(&observer);
     Mock::VerifyAndClearExpectations(&incognito_observer);
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index eb41d52..ffb8152 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -2582,16 +2582,6 @@ void ExtensionService::Observe(int type,
                      process->GetID()));
       break;
     }
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      const std::string& pref_name =
-          *content::Details<std::string>(details).ptr();
-      DCHECK(pref_name == prefs::kExtensionInstallAllowList ||
-             pref_name == prefs::kExtensionInstallDenyList)
-          << "Unexpected preference name " << pref_name;
-      IdentifyAlertableExtensions();
-      CheckManagementPolicy();
-      break;
-    }
     case chrome::NOTIFICATION_IMPORT_FINISHED: {
       InitAfterImport();
       break;
@@ -2602,6 +2592,15 @@ void ExtensionService::Observe(int type,
   }
 }
 
+void ExtensionService::OnPreferenceChanged(PrefServiceBase* service,
+                                           const std::string& pref_name) {
+  DCHECK(pref_name == prefs::kExtensionInstallAllowList ||
+         pref_name == prefs::kExtensionInstallDenyList)
+      << "Unexpected preference name " << pref_name;
+  IdentifyAlertableExtensions();
+  CheckManagementPolicy();
+}
+
 bool ExtensionService::HasApps() const {
   return !GetAppIds().empty();
 }
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index 49f029b..7b4e044 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -17,6 +17,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string16.h"
 #include "chrome/browser/extensions/app_shortcut_manager.h"
 #include "chrome/browser/extensions/app_sync_bundle.h"
@@ -140,7 +141,8 @@ class ExtensionServiceInterface : public syncer::SyncableService {
 class ExtensionService
     : public ExtensionServiceInterface,
       public extensions::ExternalProviderInterface::VisitorInterface,
-      public content::NotificationObserver {
+      public content::NotificationObserver,
+      public PrefObserver {
  public:
   // The name of the directory inside the profile where extensions are
   // installed to.
@@ -621,6 +623,10 @@ class ExtensionService
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Whether there are any apps installed. Component apps are not included.
   bool HasApps() const;
 
diff --git a/chrome/browser/extensions/external_policy_loader.cc b/chrome/browser/extensions/external_policy_loader.cc
index 5a3cbf9..79ddb8d 100644
--- a/chrome/browser/extensions/external_policy_loader.cc
+++ b/chrome/browser/extensions/external_policy_loader.cc
@@ -79,25 +79,20 @@ void ExternalPolicyLoader::Observe(
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   if (profile_ == NULL) return;
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      if (content::Source<PrefService>(source).ptr() == profile_->GetPrefs()) {
-        DCHECK_EQ(std::string(prefs::kExtensionInstallForceList),
-                  *content::Details<std::string>(details).ptr());
-        StartLoading();
-      }
-      break;
-    }
-    case chrome::NOTIFICATION_PROFILE_DESTROYED: {
-      if (content::Source<Profile>(source).ptr() == profile_) {
-        notification_registrar_.RemoveAll();
-        pref_change_registrar_.RemoveAll();
-        profile_ = NULL;
-      }
-      break;
-    }
-    default:
-      NOTREACHED() << "Unexpected notification type.";
+  DCHECK(type == chrome::NOTIFICATION_PROFILE_DESTROYED) <<
+      "Unexpected notification type.";
+  if (content::Source<Profile>(source).ptr() == profile_) {
+    notification_registrar_.RemoveAll();
+    pref_change_registrar_.RemoveAll();
+    profile_ = NULL;
+  }
+}
+
+void ExternalPolicyLoader::OnPreferenceChanged(PrefServiceBase* service,
+                                               const std::string& pref_name) {
+  if (service == profile_->GetPrefs()) {
+    DCHECK_EQ(std::string(prefs::kExtensionInstallForceList), pref_name);
+    StartLoading();
   }
 }
 
diff --git a/chrome/browser/extensions/external_policy_loader.h b/chrome/browser/extensions/external_policy_loader.h
index bd0f5f5..44f9f1b 100644
--- a/chrome/browser/extensions/external_policy_loader.h
+++ b/chrome/browser/extensions/external_policy_loader.h
@@ -9,6 +9,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
@@ -21,7 +22,8 @@ namespace extensions {
 // registered.
 class ExternalPolicyLoader
     : public ExternalLoader,
-      public content::NotificationObserver {
+      public content::NotificationObserver,
+      public PrefObserver {
  public:
   explicit ExternalPolicyLoader(Profile* profile);
 
@@ -30,6 +32,10 @@ class ExternalPolicyLoader
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
  protected:
   virtual void StartLoading() OVERRIDE;
 
diff --git a/chrome/browser/media_gallery/media_file_system_registry.cc b/chrome/browser/media_gallery/media_file_system_registry.cc
index bd1ece3..030cb4b 100644
--- a/chrome/browser/media_gallery/media_file_system_registry.cc
+++ b/chrome/browser/media_gallery/media_file_system_registry.cc
@@ -35,6 +35,7 @@
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_details.h"
+#include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
@@ -678,17 +679,12 @@ MediaFileSystemRegistry::~MediaFileSystemRegistry() {
     system_monitor->RemoveDevicesChangedObserver(this);
 }
 
-void MediaFileSystemRegistry::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  const std::string& pref_name =
-      *content::Details<std::string>(details).ptr();
+void MediaFileSystemRegistry::OnPreferenceChanged(
+    PrefServiceBase* prefs,
+    const std::string& pref_name) {
   DCHECK_EQ(std::string(prefs::kMediaGalleriesRememberedGalleries), pref_name);
 
   // Find the Profile that contains the source PrefService.
-  PrefService* prefs = content::Source<PrefService>(source).ptr();
   PrefChangeRegistrarMap::iterator pref_change_it =
       pref_change_registrar_map_.begin();
   for (; pref_change_it != pref_change_registrar_map_.end(); ++pref_change_it) {
diff --git a/chrome/browser/media_gallery/media_file_system_registry.h b/chrome/browser/media_gallery/media_file_system_registry.h
index 28825b9..bfc266d 100644
--- a/chrome/browser/media_gallery/media_file_system_registry.h
+++ b/chrome/browser/media_gallery/media_file_system_registry.h
@@ -19,8 +19,8 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/system_monitor/system_monitor.h"
-#include "content/public/browser/notification_observer.h"
 #include "webkit/fileapi/media/mtp_device_file_system_config.h"
 
 class Profile;
@@ -81,7 +81,7 @@ typedef base::Callback<void(const std::vector<MediaFileSystemInfo>&)>
 
 class MediaFileSystemRegistry
     : public base::SystemMonitor::DevicesChangedObserver,
-      public content::NotificationObserver {
+      public PrefObserver {
  public:
   // The instance is lazily created per browser process.
   static MediaFileSystemRegistry* GetInstance();
@@ -131,10 +131,9 @@ class MediaFileSystemRegistry
   MediaFileSystemRegistry();
   virtual ~MediaFileSystemRegistry();
 
-  // NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
 #if defined(SUPPORT_MTP_DEVICE_FILESYSTEM)
   // Returns ScopedMtpDeviceMapEntry object for the given |device_location|.
diff --git a/chrome/browser/net/chrome_url_request_context.cc b/chrome/browser/net/chrome_url_request_context.cc
index 8cb7c51..3130ed2 100644
--- a/chrome/browser/net/chrome_url_request_context.cc
+++ b/chrome/browser/net/chrome_url_request_context.cc
@@ -295,37 +295,29 @@ void ChromeURLRequestContextGetter::CleanupOnUIThread() {
   registrar_.RemoveAll();
 }
 
-// content::NotificationObserver implementation.
-void ChromeURLRequestContextGetter::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void ChromeURLRequestContextGetter::OnPreferenceChanged(
+    PrefServiceBase* prefs,
+    const std::string& pref_name_in) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  if (chrome::NOTIFICATION_PREF_CHANGED == type) {
-    std::string* pref_name_in = content::Details<std::string>(details).ptr();
-    PrefService* prefs = content::Source<PrefService>(source).ptr();
-    DCHECK(pref_name_in && prefs);
-    if (*pref_name_in == prefs::kAcceptLanguages) {
-      std::string accept_language =
-          prefs->GetString(prefs::kAcceptLanguages);
-      BrowserThread::PostTask(
-          BrowserThread::IO, FROM_HERE,
-          base::Bind(
-              &ChromeURLRequestContextGetter::OnAcceptLanguageChange,
-              this,
-              accept_language));
-    } else if (*pref_name_in == prefs::kDefaultCharset) {
-      std::string default_charset = prefs->GetString(prefs::kDefaultCharset);
-      BrowserThread::PostTask(
-          BrowserThread::IO, FROM_HERE,
-          base::Bind(
-              &ChromeURLRequestContextGetter::OnDefaultCharsetChange,
-              this,
-              default_charset));
-    }
-  } else {
-    NOTREACHED();
+  DCHECK(prefs);
+  if (pref_name_in == prefs::kAcceptLanguages) {
+    std::string accept_language =
+        prefs->GetString(prefs::kAcceptLanguages);
+    BrowserThread::PostTask(
+        BrowserThread::IO, FROM_HERE,
+        base::Bind(
+            &ChromeURLRequestContextGetter::OnAcceptLanguageChange,
+            this,
+            accept_language));
+  } else if (pref_name_in == prefs::kDefaultCharset) {
+    std::string default_charset = prefs->GetString(prefs::kDefaultCharset);
+    BrowserThread::PostTask(
+        BrowserThread::IO, FROM_HERE,
+        base::Bind(
+            &ChromeURLRequestContextGetter::OnDefaultCharsetChange,
+            this,
+            default_charset));
   }
 }
 
diff --git a/chrome/browser/net/chrome_url_request_context.h b/chrome/browser/net/chrome_url_request_context.h
index 93398e1..90ee941 100644
--- a/chrome/browser/net/chrome_url_request_context.h
+++ b/chrome/browser/net/chrome_url_request_context.h
@@ -9,8 +9,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_context_getter.h"
 #include "net/url_request/url_request_job_factory.h"
@@ -100,7 +99,7 @@ class ChromeURLRequestContext : public net::URLRequestContext {
 // Most methods are expected to be called on the UI thread, except for
 // the destructor and GetURLRequestContext().
 class ChromeURLRequestContextGetter : public net::URLRequestContextGetter,
-                                      public content::NotificationObserver {
+                                      public PrefObserver {
  public:
   // Constructs a ChromeURLRequestContextGetter that will use |factory| to
   // create the ChromeURLRequestContext. If |profile| is non-NULL, then the
@@ -181,10 +180,9 @@ class ChromeURLRequestContextGetter : public net::URLRequestContextGetter,
   // thread before the instance is deleted on the IO thread.
   void CleanupOnUIThread();
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   // Must be called on the IO thread.
diff --git a/chrome/browser/net/http_server_properties_manager.cc b/chrome/browser/net/http_server_properties_manager.cc
index 94e4e02..02a173f 100644
--- a/chrome/browser/net/http_server_properties_manager.cc
+++ b/chrome/browser/net/http_server_properties_manager.cc
@@ -636,16 +636,12 @@ void HttpServerPropertiesManager::UpdatePrefsOnUI(
   setting_prefs_ = false;
 }
 
-void HttpServerPropertiesManager::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void HttpServerPropertiesManager::OnPreferenceChanged(
+    PrefServiceBase* prefs,
+    const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK(type == chrome::NOTIFICATION_PREF_CHANGED);
-  PrefService* prefs = content::Source<PrefService>(source).ptr();
   DCHECK(prefs == pref_service_);
-  std::string* pref_name = content::Details<std::string>(details).ptr();
-  if (*pref_name == prefs::kHttpServerProperties) {
+  if (pref_name == prefs::kHttpServerProperties) {
     if (!setting_prefs_)
       ScheduleUpdateCacheOnUI();
   } else {
diff --git a/chrome/browser/net/http_server_properties_manager.h b/chrome/browser/net/http_server_properties_manager.h
index 43ee740..dc6a3a8 100644
--- a/chrome/browser/net/http_server_properties_manager.h
+++ b/chrome/browser/net/http_server_properties_manager.h
@@ -12,9 +12,9 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/timer.h"
 #include "base/values.h"
-#include "content/public/browser/notification_observer.h"
 #include "net/base/host_port_pair.h"
 #include "net/http/http_pipelined_host_capability.h"
 #include "net/http/http_server_properties.h"
@@ -48,7 +48,7 @@ namespace chrome_browser_net {
 // the actual update starts, and grab a WeakPtr.
 class HttpServerPropertiesManager
     : public net::HttpServerProperties,
-      public content::NotificationObserver {
+      public PrefObserver {
  public:
   // Create an instance of the HttpServerPropertiesManager. The lifetime of the
   // PrefService objects must be longer than that of the
@@ -187,9 +187,8 @@ class HttpServerPropertiesManager
 
  private:
   // Callback for preference changes.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // ---------
   // UI thread
diff --git a/chrome/browser/net/net_pref_observer.cc b/chrome/browser/net/net_pref_observer.cc
index 4ccf194..e985609 100644
--- a/chrome/browser/net/net_pref_observer.cc
+++ b/chrome/browser/net/net_pref_observer.cc
@@ -34,10 +34,8 @@ NetPrefObserver::~NetPrefObserver() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 }
 
-void NetPrefObserver::Observe(int type,
-                              const content::NotificationSource& source,
-                              const content::NotificationDetails& details) {
-  DCHECK_EQ(type, chrome::NOTIFICATION_PREF_CHANGED);
+void NetPrefObserver::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
   ApplySettings();
 }
 
diff --git a/chrome/browser/net/net_pref_observer.h b/chrome/browser/net/net_pref_observer.h
index 5f3157e..1d2f577 100644
--- a/chrome/browser/net/net_pref_observer.h
+++ b/chrome/browser/net/net_pref_observer.h
@@ -6,8 +6,8 @@
 #define CHROME_BROWSER_NET_NET_PREF_OBSERVER_H_
 
 #include "base/basictypes.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
-#include "content/public/browser/notification_observer.h"
 
 namespace chrome_browser_net {
 class Predictor;
@@ -22,7 +22,7 @@ class PrefService;
 // Monitors network-related preferences for changes and applies them.
 // The supplied PrefService must outlive this NetPrefObserver.
 // Must be used only on the UI thread.
-class NetPrefObserver : public content::NotificationObserver {
+class NetPrefObserver : public PrefObserver {
  public:
   // |prefs| must be non-NULL and |*prefs| must outlive this.
   // |prerender_manager| may be NULL. If not, |*prerender_manager| must
@@ -32,10 +32,9 @@ class NetPrefObserver : public content::NotificationObserver {
                   chrome_browser_net::Predictor* predictor);
   virtual ~NetPrefObserver();
 
-  // content::NotificationObserver
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   static void RegisterPrefs(PrefService* prefs);
 
diff --git a/chrome/browser/net/pref_proxy_config_tracker_impl.cc b/chrome/browser/net/pref_proxy_config_tracker_impl.cc
index 9760f02..50398ab 100644
--- a/chrome/browser/net/pref_proxy_config_tracker_impl.cc
+++ b/chrome/browser/net/pref_proxy_config_tracker_impl.cc
@@ -287,13 +287,11 @@ bool PrefProxyConfigTrackerImpl::PrefConfigToNetConfig(
   return false;
 }
 
-void PrefProxyConfigTrackerImpl::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void PrefProxyConfigTrackerImpl::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  if (type == chrome::NOTIFICATION_PREF_CHANGED &&
-      content::Source<PrefService>(source).ptr() == pref_service_) {
+  if (service == pref_service_) {
     net::ProxyConfig new_config;
     ProxyPrefs::ConfigState config_state = ReadPrefConfig(&new_config);
     if (config_state_ != config_state ||
@@ -307,7 +305,7 @@ void PrefProxyConfigTrackerImpl::Observe(
     if (update_pending_)
       OnProxyConfigChanged(config_state, new_config);
   } else {
-    NOTREACHED() << "Unexpected notification of type " << type;
+    NOTREACHED() << "Unexpected PrefService.";
   }
 }
 
diff --git a/chrome/browser/net/pref_proxy_config_tracker_impl.h b/chrome/browser/net/pref_proxy_config_tracker_impl.h
index 6df5c75..7ec829e 100644
--- a/chrome/browser/net/pref_proxy_config_tracker_impl.h
+++ b/chrome/browser/net/pref_proxy_config_tracker_impl.h
@@ -10,8 +10,8 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/prefs/proxy_config_dictionary.h"
-#include "content/public/browser/notification_observer.h"
 #include "net/proxy/proxy_config.h"
 #include "net/proxy/proxy_config_service.h"
 
@@ -78,7 +78,7 @@ class ChromeProxyConfigService
 // A class that tracks proxy preferences. It translates the configuration
 // to net::ProxyConfig and pushes the result over to the IO thread for
 // ChromeProxyConfigService::UpdateProxyConfig to use.
-class PrefProxyConfigTrackerImpl : public content::NotificationObserver {
+class PrefProxyConfigTrackerImpl : public PrefObserver {
  public:
   explicit PrefProxyConfigTrackerImpl(PrefService* pref_service);
   virtual ~PrefProxyConfigTrackerImpl();
@@ -132,10 +132,9 @@ class PrefProxyConfigTrackerImpl : public content::NotificationObserver {
   virtual void OnProxyConfigChanged(ProxyPrefs::ConfigState config_state,
                                     const net::ProxyConfig& config);
 
-  // content::NotificationObserver implementation:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
 
   const PrefService* prefs() const { return pref_service_; }
diff --git a/chrome/browser/net/ssl_config_service_manager_pref.cc b/chrome/browser/net/ssl_config_service_manager_pref.cc
index 86cc792..28d769c 100644
--- a/chrome/browser/net/ssl_config_service_manager_pref.cc
+++ b/chrome/browser/net/ssl_config_service_manager_pref.cc
@@ -10,6 +10,7 @@
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/content_settings/content_settings_utils.h"
 #include "chrome/browser/prefs/pref_service.h"
@@ -17,8 +18,6 @@
 #include "chrome/common/content_settings.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
-#include "content/public/browser/notification_details.h"
-#include "content/public/browser/notification_source.h"
 #include "net/base/ssl_cipher_suite_names.h"
 #include "net/base/ssl_config_service.h"
 
@@ -145,7 +144,7 @@ void SSLConfigServicePref::SetNewSSLConfig(
 // The manager for holding and updating an SSLConfigServicePref instance.
 class SSLConfigServiceManagerPref
     : public SSLConfigServiceManager,
-      public content::NotificationObserver {
+      public PrefObserver {
  public:
   SSLConfigServiceManagerPref(PrefService* local_state,
                               PrefService* user_prefs);
@@ -159,9 +158,8 @@ class SSLConfigServiceManagerPref
  private:
   // Callback for preference changes.  This will post the changes to the IO
   // thread with SetNewSSLConfig.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details);
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Store SSL config settings in |config|, directly from the preferences. Must
   // only be called from UI thread.
@@ -169,10 +167,10 @@ class SSLConfigServiceManagerPref
 
   // Processes changes to the disabled cipher suites preference, updating the
   // cached list of parsed SSL/TLS cipher suites that are disabled.
-  void OnDisabledCipherSuitesChange(PrefService* local_state);
+  void OnDisabledCipherSuitesChange(PrefServiceBase* local_state);
 
   // Processes changes to the default cookie settings.
-  void OnDefaultContentSettingsChange(PrefService* user_prefs);
+  void OnDefaultContentSettingsChange(PrefServiceBase* user_prefs);
 
   PrefChangeRegistrar local_state_change_registrar_;
   PrefChangeRegistrar user_prefs_change_registrar_;
@@ -255,33 +253,28 @@ net::SSLConfigService* SSLConfigServiceManagerPref::Get() {
   return ssl_config_service_;
 }
 
-void SSLConfigServiceManagerPref::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-    std::string* pref_name_in = content::Details<std::string>(details).ptr();
-    PrefService* prefs = content::Source<PrefService>(source).ptr();
-    DCHECK(pref_name_in && prefs);
-    if (*pref_name_in == prefs::kCipherSuiteBlacklist)
-      OnDisabledCipherSuitesChange(prefs);
-    else if (*pref_name_in == prefs::kDefaultContentSettings)
-      OnDefaultContentSettingsChange(prefs);
-
-    net::SSLConfig new_config;
-    GetSSLConfigFromPrefs(&new_config);
-
-    // Post a task to |io_loop| with the new configuration, so it can
-    // update |cached_config_|.
-    BrowserThread::PostTask(
-        BrowserThread::IO,
-        FROM_HERE,
-        base::Bind(
-            &SSLConfigServicePref::SetNewSSLConfig,
-            ssl_config_service_.get(),
-            new_config));
-  }
+void SSLConfigServiceManagerPref::OnPreferenceChanged(
+    PrefServiceBase* prefs,
+    const std::string& pref_name_in) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(prefs);
+  if (pref_name_in == prefs::kCipherSuiteBlacklist)
+    OnDisabledCipherSuitesChange(prefs);
+  else if (pref_name_in == prefs::kDefaultContentSettings)
+    OnDefaultContentSettingsChange(prefs);
+
+  net::SSLConfig new_config;
+  GetSSLConfigFromPrefs(&new_config);
+
+  // Post a task to |io_loop| with the new configuration, so it can
+  // update |cached_config_|.
+  BrowserThread::PostTask(
+      BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(
+          &SSLConfigServicePref::SetNewSSLConfig,
+          ssl_config_service_.get(),
+          new_config));
 }
 
 void SSLConfigServiceManagerPref::GetSSLConfigFromPrefs(
@@ -318,13 +311,13 @@ void SSLConfigServiceManagerPref::GetSSLConfigFromPrefs(
 }
 
 void SSLConfigServiceManagerPref::OnDisabledCipherSuitesChange(
-    PrefService* local_state) {
+    PrefServiceBase* local_state) {
   const ListValue* value = local_state->GetList(prefs::kCipherSuiteBlacklist);
   disabled_cipher_suites_ = ParseCipherSuites(ListValueToStringVector(value));
 }
 
 void SSLConfigServiceManagerPref::OnDefaultContentSettingsChange(
-    PrefService* user_prefs) {
+    PrefServiceBase* user_prefs) {
   const DictionaryValue* value = user_prefs->GetDictionary(
       prefs::kDefaultContentSettings);
   int default_cookie_settings = -1;
diff --git a/chrome/browser/notifications/notification_ui_manager_impl.cc b/chrome/browser/notifications/notification_ui_manager_impl.cc
index f02b0f5..bf096c3 100644
--- a/chrome/browser/notifications/notification_ui_manager_impl.cc
+++ b/chrome/browser/notifications/notification_ui_manager_impl.cc
@@ -233,13 +233,17 @@ void NotificationUIManagerImpl::Observe(
     const content::NotificationDetails& details) {
   if (type == chrome::NOTIFICATION_APP_TERMINATING) {
     CancelAll();
-  } else if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* name = content::Details<std::string>(details).ptr();
-    if (*name == prefs::kDesktopNotificationPosition)
-      balloon_collection_->SetPositionPreference(
-          static_cast<BalloonCollection::PositionPreference>(
-              position_pref_.GetValue()));
   } else {
     NOTREACHED();
   }
 }
+
+void NotificationUIManagerImpl::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  if (pref_name == prefs::kDesktopNotificationPosition) {
+    balloon_collection_->SetPositionPreference(
+        static_cast<BalloonCollection::PositionPreference>(
+            position_pref_.GetValue()));
+  }
+}
diff --git a/chrome/browser/notifications/notification_ui_manager_impl.h b/chrome/browser/notifications/notification_ui_manager_impl.h
index e313622..0adebdf 100644
--- a/chrome/browser/notifications/notification_ui_manager_impl.h
+++ b/chrome/browser/notifications/notification_ui_manager_impl.h
@@ -11,6 +11,7 @@
 
 #include "base/id_map.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/timer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/notifications/balloon.h"
@@ -31,7 +32,8 @@ class NotificationUIManagerImpl
     : public NotificationUIManager,
       public NotificationPrefsManager,
       public BalloonCollection::BalloonSpaceChangeListener,
-      public content::NotificationObserver {
+      public content::NotificationObserver,
+      public PrefObserver {
  public:
   explicit NotificationUIManagerImpl(PrefService* local_state);
   virtual ~NotificationUIManagerImpl();
@@ -63,6 +65,10 @@ class NotificationUIManagerImpl
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver override.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Attempts to display notifications from the show_queue if the user
   // is active.
   void CheckAndShowNotifications();
diff --git a/chrome/browser/plugins/plugin_prefs.cc b/chrome/browser/plugins/plugin_prefs.cc
index ecb63d1..d8ee038 100644
--- a/chrome/browser/plugins/plugin_prefs.cc
+++ b/chrome/browser/plugins/plugin_prefs.cc
@@ -274,26 +274,19 @@ bool PluginPrefs::IsPluginEnabled(const webkit::WebPluginInfo& plugin) const {
   return true;
 }
 
-void PluginPrefs::Observe(int type,
-                          const content::NotificationSource& source,
-                          const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  const std::string* pref_name = content::Details<std::string>(details).ptr();
-  if (!pref_name) {
-    NOTREACHED();
-    return;
-  }
-  DCHECK_EQ(prefs_, content::Source<PrefService>(source).ptr());
-  if (*pref_name == prefs::kPluginsDisabledPlugins) {
+void PluginPrefs::OnPreferenceChanged(PrefServiceBase* service,
+                                      const std::string& pref_name) {
+  DCHECK_EQ(prefs_, service);
+  if (pref_name == prefs::kPluginsDisabledPlugins) {
     base::AutoLock auto_lock(lock_);
     ListValueToStringSet(prefs_->GetList(prefs::kPluginsDisabledPlugins),
                          &policy_disabled_plugin_patterns_);
-  } else if (*pref_name == prefs::kPluginsDisabledPluginsExceptions) {
+  } else if (pref_name == prefs::kPluginsDisabledPluginsExceptions) {
     base::AutoLock auto_lock(lock_);
     ListValueToStringSet(
         prefs_->GetList(prefs::kPluginsDisabledPluginsExceptions),
         &policy_disabled_plugin_exception_patterns_);
-  } else if (*pref_name == prefs::kPluginsEnabledPlugins) {
+  } else if (pref_name == prefs::kPluginsEnabledPlugins) {
     base::AutoLock auto_lock(lock_);
     ListValueToStringSet(prefs_->GetList(prefs::kPluginsEnabledPlugins),
                          &policy_enabled_plugin_patterns_);
diff --git a/chrome/browser/plugins/plugin_prefs.h b/chrome/browser/plugins/plugin_prefs.h
index 95fe301..594e3d3 100644
--- a/chrome/browser/plugins/plugin_prefs.h
+++ b/chrome/browser/plugins/plugin_prefs.h
@@ -12,11 +12,11 @@
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/synchronization/lock.h"
 #include "chrome/browser/plugins/plugin_finder.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/refcounted_profile_keyed_service.h"
-#include "content/public/browser/notification_observer.h"
 
 class Profile;
 
@@ -35,7 +35,7 @@ class PluginList;
 // enabled or disabled.
 // Except where otherwise noted, it can be used on every thread.
 class PluginPrefs : public RefcountedProfileKeyedService,
-                    public content::NotificationObserver {
+                    public PrefObserver {
  public:
   enum PolicyStatus {
     NO_POLICY = 0,  // Neither enabled or disabled by policy.
@@ -85,10 +85,9 @@ class PluginPrefs : public RefcountedProfileKeyedService,
   // RefCountedProfileKeyedBase method override.
   virtual void ShutdownOnUIThread() OVERRIDE;
 
-  // content::NotificationObserver method override.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver method override.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   friend class base::RefCountedThreadSafe<PluginPrefs>;
diff --git a/chrome/browser/plugins/plugin_status_pref_setter.cc b/chrome/browser/plugins/plugin_status_pref_setter.cc
index dc3a91a..2de8547 100644
--- a/chrome/browser/plugins/plugin_status_pref_setter.cc
+++ b/chrome/browser/plugins/plugin_status_pref_setter.cc
@@ -28,7 +28,7 @@ PluginStatusPrefSetter::~PluginStatusPrefSetter() {
 }
 
 void PluginStatusPrefSetter::Init(Profile* profile,
-                                  content::NotificationObserver* observer) {
+                                  PrefObserver* observer) {
   clear_plugin_lso_data_enabled_.Init(prefs::kClearPluginLSODataEnabled,
                                       profile->GetPrefs(), observer);
   pepper_flash_settings_enabled_.Init(prefs::kPepperFlashSettingsEnabled,
diff --git a/chrome/browser/plugins/plugin_status_pref_setter.h b/chrome/browser/plugins/plugin_status_pref_setter.h
index ab406ae..915a820 100644
--- a/chrome/browser/plugins/plugin_status_pref_setter.h
+++ b/chrome/browser/plugins/plugin_status_pref_setter.h
@@ -9,6 +9,7 @@
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -34,8 +35,7 @@ class PluginStatusPrefSetter : public content::NotificationObserver {
   // any value changes.
   // This asynchronously calls the PluginService to get the list of installed
   // plug-ins.
-  void Init(Profile* profile,
-            content::NotificationObserver* observer);
+  void Init(Profile* profile, PrefObserver* observer);
 
   bool IsClearPluginLSODataEnabled() const {
     return clear_plugin_lso_data_enabled_.GetValue();
diff --git a/chrome/browser/policy/cloud_policy_refresh_scheduler.cc b/chrome/browser/policy/cloud_policy_refresh_scheduler.cc
index a0d9821..6397f8e 100644
--- a/chrome/browser/policy/cloud_policy_refresh_scheduler.cc
+++ b/chrome/browser/policy/cloud_policy_refresh_scheduler.cc
@@ -99,13 +99,10 @@ void CloudPolicyRefreshScheduler::OnStoreError(CloudPolicyStore* store) {
   // error is required. NB: Changes to is_managed fire OnStoreLoaded().
 }
 
-void CloudPolicyRefreshScheduler::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(refresh_delay_.GetPrefName(),
-            *content::Details<std::string>(details).ptr());
+void CloudPolicyRefreshScheduler::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  DCHECK_EQ(refresh_delay_.GetPrefName(), pref_name);
 
   ScheduleRefresh();
 }
diff --git a/chrome/browser/policy/cloud_policy_refresh_scheduler.h b/chrome/browser/policy/cloud_policy_refresh_scheduler.h
index 2b4ea13..aaba6c1 100644
--- a/chrome/browser/policy/cloud_policy_refresh_scheduler.h
+++ b/chrome/browser/policy/cloud_policy_refresh_scheduler.h
@@ -10,11 +10,11 @@
 #include "base/basictypes.h"
 #include "base/cancelable_callback.h"
 #include "base/memory/ref_counted.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/time.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/policy/cloud_policy_client.h"
 #include "chrome/browser/policy/cloud_policy_store.h"
-#include "content/public/browser/notification_observer.h"
 #include "net/base/network_change_notifier.h"
 
 class PrefService;
@@ -30,7 +30,7 @@ namespace policy {
 class CloudPolicyRefreshScheduler
     : public CloudPolicyClient::Observer,
       public CloudPolicyStore::Observer,
-      public content::NotificationObserver,
+      public PrefObserver,
       public net::NetworkChangeNotifier::IPAddressObserver {
  public:
   // Refresh constants.
@@ -60,10 +60,9 @@ class CloudPolicyRefreshScheduler
   virtual void OnStoreLoaded(CloudPolicyStore* store) OVERRIDE;
   virtual void OnStoreError(CloudPolicyStore* store) OVERRIDE;
 
-  // content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // net::NetworkChangeNotifier::IPAddressObserver:
   virtual void OnIPAddressChanged() OVERRIDE;
diff --git a/chrome/browser/policy/cloud_policy_subsystem.cc b/chrome/browser/policy/cloud_policy_subsystem.cc
index bc51d67..a937508 100644
--- a/chrome/browser/policy/cloud_policy_subsystem.cc
+++ b/chrome/browser/policy/cloud_policy_subsystem.cc
@@ -158,19 +158,12 @@ void CloudPolicySubsystem::UpdatePolicyRefreshRate(int64 refresh_rate) {
   }
 }
 
-void CloudPolicySubsystem::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    DCHECK_EQ(*(content::Details<std::string>(details).ptr()),
-              std::string(refresh_pref_name_));
-    PrefService* local_state = g_browser_process->local_state();
-    DCHECK_EQ(content::Source<PrefService>(source).ptr(), local_state);
-    UpdatePolicyRefreshRate(local_state->GetInteger(refresh_pref_name_));
-  } else {
-    NOTREACHED();
-  }
+void CloudPolicySubsystem::OnPreferenceChanged(PrefServiceBase* service,
+                                               const std::string& pref_name) {
+  DCHECK_EQ(pref_name, refresh_pref_name_);
+  PrefService* local_state = g_browser_process->local_state();
+  DCHECK_EQ(service, local_state);
+  UpdatePolicyRefreshRate(local_state->GetInteger(refresh_pref_name_));
 }
 
 void CloudPolicySubsystem::ScheduleServiceInitialization(
diff --git a/chrome/browser/policy/cloud_policy_subsystem.h b/chrome/browser/policy/cloud_policy_subsystem.h
index fd81072..2ff3eab 100644
--- a/chrome/browser/policy/cloud_policy_subsystem.h
+++ b/chrome/browser/policy/cloud_policy_subsystem.h
@@ -7,7 +7,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
-#include "content/public/browser/notification_observer.h"
+#include "base/prefs/public/pref_observer.h"
 #include "net/base/network_change_notifier.h"
 
 class PrefService;
@@ -25,7 +25,7 @@ class PolicyNotifier;
 // policy. It glues together the backend, the policy controller and manages the
 // life cycle of the policy providers.
 class CloudPolicySubsystem
-    : public content::NotificationObserver,
+    : public PrefObserver,
       public net::NetworkChangeNotifier::IPAddressObserver {
  public:
   enum PolicySubsystemState {
@@ -131,10 +131,9 @@ class CloudPolicySubsystem
   virtual void CreateDeviceTokenFetcher();
   virtual void CreateCloudPolicyController();
 
-  // content::NotificationObserver overrides.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver overrides.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // net::NetworkChangeNotifier::IPAddressObserver:
   virtual void OnIPAddressChanged() OVERRIDE;
diff --git a/chrome/browser/policy/url_blacklist_manager.cc b/chrome/browser/policy/url_blacklist_manager.cc
index 2235792..d175ebf 100644
--- a/chrome/browser/policy/url_blacklist_manager.cc
+++ b/chrome/browser/policy/url_blacklist_manager.cc
@@ -297,16 +297,12 @@ void URLBlacklistManager::ShutdownOnUIThread() {
 URLBlacklistManager::~URLBlacklistManager() {
 }
 
-void URLBlacklistManager::Observe(int type,
-                                  const content::NotificationSource& source,
-                                  const content::NotificationDetails& details) {
+void URLBlacklistManager::OnPreferenceChanged(PrefServiceBase* prefs,
+                                              const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK(type == chrome::NOTIFICATION_PREF_CHANGED);
-  PrefService* prefs = content::Source<PrefService>(source).ptr();
   DCHECK(prefs == pref_service_);
-  std::string* pref_name = content::Details<std::string>(details).ptr();
-  DCHECK(*pref_name == prefs::kUrlBlacklist ||
-         *pref_name == prefs::kUrlWhitelist);
+  DCHECK(pref_name == prefs::kUrlBlacklist ||
+         pref_name == prefs::kUrlWhitelist);
   ScheduleUpdate();
 }
 
diff --git a/chrome/browser/policy/url_blacklist_manager.h b/chrome/browser/policy/url_blacklist_manager.h
index 8582b9f..9bbf47c 100644
--- a/chrome/browser/policy/url_blacklist_manager.h
+++ b/chrome/browser/policy/url_blacklist_manager.h
@@ -15,8 +15,8 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/common/extensions/matcher/url_matcher.h"
-#include "content/public/browser/notification_observer.h"
 
 class GURL;
 class PrefService;
@@ -113,7 +113,7 @@ class URLBlacklist {
 // exists in UI, then a potential destruction on IO will come after any task
 // posted to IO from that method on UI. This is used to go through IO before
 // the actual update starts, and grab a WeakPtr.
-class URLBlacklistManager : public content::NotificationObserver {
+class URLBlacklistManager : public PrefObserver {
  public:
   // Must be constructed on the UI thread.
   explicit URLBlacklistManager(PrefService* pref_service);
@@ -148,9 +148,8 @@ class URLBlacklistManager : public content::NotificationObserver {
                   scoped_ptr<base::ListValue> allow);
 
  private:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // ---------
   // UI thread
diff --git a/chrome/browser/prefs/DEPS b/chrome/browser/prefs/DEPS
new file mode 100644
index 0000000..6cd8260
--- /dev/null
+++ b/chrome/browser/prefs/DEPS
@@ -0,0 +1,11 @@
+include_rules = [
+  "-content",
+]
+
+specific_include_rules = {
+  "pref_service.*|browser_prefs.*": [
+    "+content/public/browser/browser_thread.h",
+    "+content/public/browser/render_process_host.h",
+    "+content/public/test",
+  ],
+}
diff --git a/chrome/browser/prefs/pref_notifier_impl.cc b/chrome/browser/prefs/pref_notifier_impl.cc
index a226685..9bdf322 100644
--- a/chrome/browser/prefs/pref_notifier_impl.cc
+++ b/chrome/browser/prefs/pref_notifier_impl.cc
@@ -7,9 +7,6 @@
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "chrome/browser/prefs/pref_service.h"
-#include "chrome/common/chrome_notification_types.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_service.h"
 
 PrefNotifierImpl::PrefNotifierImpl()
     : pref_service_(NULL) {
@@ -25,45 +22,42 @@ PrefNotifierImpl::~PrefNotifierImpl() {
   // Verify that there are no pref observers when we shut down.
   for (PrefObserverMap::iterator it = pref_observers_.begin();
        it != pref_observers_.end(); ++it) {
-    NotificationObserverList::Iterator obs_iterator(*(it->second));
+    PrefObserverList::Iterator obs_iterator(*(it->second));
     if (obs_iterator.GetNext()) {
       LOG(WARNING) << "pref observer found at shutdown " << it->first;
     }
   }
 
+  // Same for initialization observers.
+  if (!init_observers_.empty())
+    LOG(WARNING) << "Init observer found at shutdown.";
+
   STLDeleteContainerPairSecondPointers(pref_observers_.begin(),
                                        pref_observers_.end());
   pref_observers_.clear();
+  init_observers_.clear();
 }
 
 void PrefNotifierImpl::AddPrefObserver(const char* path,
-                                       content::NotificationObserver* obs) {
+                                       PrefObserver* obs) {
   // Get the pref observer list associated with the path.
-  NotificationObserverList* observer_list = NULL;
+  PrefObserverList* observer_list = NULL;
   const PrefObserverMap::iterator observer_iterator =
       pref_observers_.find(path);
   if (observer_iterator == pref_observers_.end()) {
-    observer_list = new NotificationObserverList;
+    observer_list = new PrefObserverList;
     pref_observers_[path] = observer_list;
   } else {
     observer_list = observer_iterator->second;
   }
 
-  // Verify that this observer doesn't already exist.
-  NotificationObserverList::Iterator it(*observer_list);
-  content::NotificationObserver* existing_obs;
-  while ((existing_obs = it.GetNext()) != NULL) {
-    DCHECK(existing_obs != obs) << path << " observer already registered";
-    if (existing_obs == obs)
-      return;
-  }
-
-  // Ok, safe to add the pref observer.
+  // Add the pref observer. ObserverList will DCHECK if it already is
+  // in the list.
   observer_list->AddObserver(obs);
 }
 
 void PrefNotifierImpl::RemovePrefObserver(const char* path,
-                                          content::NotificationObserver* obs) {
+                                          PrefObserver* obs) {
   DCHECK(CalledOnValidThread());
 
   const PrefObserverMap::iterator observer_iterator =
@@ -72,10 +66,14 @@ void PrefNotifierImpl::RemovePrefObserver(const char* path,
     return;
   }
 
-  NotificationObserverList* observer_list = observer_iterator->second;
+  PrefObserverList* observer_list = observer_iterator->second;
   observer_list->RemoveObserver(obs);
 }
 
+void PrefNotifierImpl::AddInitObserver(base::Callback<void(bool)> obs) {
+  init_observers_.push_back(obs);
+}
+
 void PrefNotifierImpl::OnPreferenceChanged(const std::string& path) {
   FireObservers(path);
 }
@@ -83,10 +81,17 @@ void PrefNotifierImpl::OnPreferenceChanged(const std::string& path) {
 void PrefNotifierImpl::OnInitializationCompleted(bool succeeded) {
   DCHECK(CalledOnValidThread());
 
-  content::NotificationService::current()->Notify(
-      chrome::NOTIFICATION_PREF_INITIALIZATION_COMPLETED,
-      content::Source<PrefService>(pref_service_),
-      content::Details<bool>(&succeeded));
+  // We must make a copy of init_observers_ and clear it before we run
+  // observers, or we can end up in this method re-entrantly before
+  // clearing the observers list.
+  PrefInitObserverList observers(init_observers_);
+  init_observers_.clear();
+
+  for (PrefInitObserverList::iterator it = observers.begin();
+       it != observers.end();
+       ++it) {
+    it->Run(succeeded);
+  }
 }
 
 void PrefNotifierImpl::FireObservers(const std::string& path) {
@@ -101,13 +106,9 @@ void PrefNotifierImpl::FireObservers(const std::string& path) {
   if (observer_iterator == pref_observers_.end())
     return;
 
-  NotificationObserverList::Iterator it(*(observer_iterator->second));
-  content::NotificationObserver* observer;
-  while ((observer = it.GetNext()) != NULL) {
-    observer->Observe(chrome::NOTIFICATION_PREF_CHANGED,
-                      content::Source<PrefService>(pref_service_),
-                      content::Details<const std::string>(&path));
-  }
+  FOR_EACH_OBSERVER(PrefObserver,
+                    *(observer_iterator->second),
+                    OnPreferenceChanged(pref_service_, path));
 }
 
 void PrefNotifierImpl::SetPrefService(PrefService* pref_service) {
diff --git a/chrome/browser/prefs/pref_notifier_impl.h b/chrome/browser/prefs/pref_notifier_impl.h
index 38255ba..34c225f 100644
--- a/chrome/browser/prefs/pref_notifier_impl.h
+++ b/chrome/browser/prefs/pref_notifier_impl.h
@@ -5,19 +5,18 @@
 #ifndef CHROME_BROWSER_PREFS_PREF_NOTIFIER_IMPL_H_
 #define CHROME_BROWSER_PREFS_PREF_NOTIFIER_IMPL_H_
 
+#include <list>
 #include <string>
 
+#include "base/callback.h"
 #include "base/hash_tables.h"
 #include "base/observer_list.h"
 #include "base/prefs/pref_notifier.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/threading/non_thread_safe.h"
 
 class PrefService;
 
-namespace content {
-class NotificationObserver;
-}
-
 // The PrefNotifier implementation used by the PrefService.
 class PrefNotifierImpl : public PrefNotifier,
                          public base::NonThreadSafe {
@@ -26,24 +25,30 @@ class PrefNotifierImpl : public PrefNotifier,
   explicit PrefNotifierImpl(PrefService* pref_service);
   virtual ~PrefNotifierImpl();
 
-  // If the pref at the given path changes, we call the observer's Observe
-  // method with PREF_CHANGED.
-  void AddPrefObserver(const char* path, content::NotificationObserver* obs);
-  void RemovePrefObserver(const char* path, content::NotificationObserver* obs);
+  // If the pref at the given path changes, we call the observer's
+  // OnPreferenceChanged method.
+  void AddPrefObserver(const char* path, PrefObserver* observer);
+  void RemovePrefObserver(const char* path, PrefObserver* observer);
 
-  // PrefNotifier overrides.
-  virtual void OnPreferenceChanged(const std::string& pref_name) OVERRIDE;
-  virtual void OnInitializationCompleted(bool succeeded) OVERRIDE;
+  // We run the callback once, when initialization completes. The bool
+  // parameter will be set to true for successful initialization,
+  // false for unsuccessful.
+  void AddInitObserver(base::Callback<void(bool)> observer);
 
   void SetPrefService(PrefService* pref_service);
 
  protected:
+  // PrefNotifier overrides.
+  virtual void OnPreferenceChanged(const std::string& pref_name) OVERRIDE;
+  virtual void OnInitializationCompleted(bool succeeded) OVERRIDE;
+
   // A map from pref names to a list of observers. Observers get fired in the
   // order they are added. These should only be accessed externally for unit
   // testing.
-  typedef ObserverList<content::NotificationObserver> NotificationObserverList;
-  typedef base::hash_map<std::string, NotificationObserverList*>
-      PrefObserverMap;
+  typedef ObserverList<PrefObserver> PrefObserverList;
+  typedef base::hash_map<std::string, PrefObserverList*> PrefObserverMap;
+
+  typedef std::list<base::Callback<void(bool)> > PrefInitObserverList;
 
   const PrefObserverMap* pref_observers() const { return &pref_observers_; }
 
@@ -56,6 +61,7 @@ class PrefNotifierImpl : public PrefNotifier,
   PrefService* pref_service_;
 
   PrefObserverMap pref_observers_;
+  PrefInitObserverList init_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefNotifierImpl);
 };
diff --git a/chrome/browser/prefs/pref_notifier_impl_unittest.cc b/chrome/browser/prefs/pref_notifier_impl_unittest.cc
index 6a5388e..4c5211e 100644
--- a/chrome/browser/prefs/pref_notifier_impl_unittest.cc
+++ b/chrome/browser/prefs/pref_notifier_impl_unittest.cc
@@ -2,16 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/prefs/pref_notifier_impl.h"
 #include "chrome/browser/prefs/pref_observer_mock.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/prefs/pref_value_store.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/test/base/testing_pref_service.h"
-#include "content/public/browser/notification_details.h"
-#include "content/public/browser/notification_registrar.h"
-#include "content/public/browser/notification_source.h"
-#include "content/public/test/mock_notification_observer.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -26,7 +25,22 @@ namespace {
 const char kChangedPref[] = "changed_pref";
 const char kUnchangedPref[] = "unchanged_pref";
 
-// Test PrefNotifier that allows tracking of observers and notifications.
+class MockPrefInitObserver {
+ public:
+  MOCK_METHOD1(OnInitializationCompleted, void(bool));
+};
+
+// This is an unmodified PrefNotifierImpl, except we make
+// OnPreferenceChanged public for tests.
+class TestingPrefNotifierImpl : public PrefNotifierImpl {
+ public:
+  TestingPrefNotifierImpl(PrefService* service) : PrefNotifierImpl(service) {}
+
+  // Make public for tests.
+  using PrefNotifierImpl::OnPreferenceChanged;
+};
+
+// Mock PrefNotifier that allows tracking of observers and notifications.
 class MockPrefNotifier : public PrefNotifierImpl {
  public:
   explicit MockPrefNotifier(PrefService* pref_service)
@@ -35,15 +49,15 @@ class MockPrefNotifier : public PrefNotifierImpl {
 
   MOCK_METHOD1(FireObservers, void(const std::string& path));
 
-  size_t CountObserver(const char* path, content::NotificationObserver* obs) {
+  size_t CountObserver(const char* path, PrefObserver* obs) {
     PrefObserverMap::const_iterator observer_iterator =
         pref_observers()->find(path);
     if (observer_iterator == pref_observers()->end())
       return false;
 
-    NotificationObserverList* observer_list = observer_iterator->second;
-    NotificationObserverList::Iterator it(*observer_list);
-    content::NotificationObserver* existing_obs;
+    PrefObserverList* observer_list = observer_iterator->second;
+    PrefObserverList::Iterator it(*observer_list);
+    PrefObserver* existing_obs;
     size_t count = 0;
     while ((existing_obs = it.GetNext()) != NULL) {
       if (existing_obs == obs)
@@ -52,6 +66,10 @@ class MockPrefNotifier : public PrefNotifierImpl {
 
     return count;
   }
+
+  // Make public for tests below.
+  using PrefNotifierImpl::OnPreferenceChanged;
+  using PrefNotifierImpl::OnInitializationCompleted;
 };
 
 // Test fixture class.
@@ -80,14 +98,11 @@ TEST_F(PrefNotifierTest, OnPreferenceChanged) {
 
 TEST_F(PrefNotifierTest, OnInitializationCompleted) {
   MockPrefNotifier notifier(&pref_service_);
-  content::MockNotificationObserver observer;
-  content::NotificationRegistrar registrar;
-  registrar.Add(&observer, chrome::NOTIFICATION_PREF_INITIALIZATION_COMPLETED,
-                content::Source<PrefService>(&pref_service_));
-  EXPECT_CALL(observer, Observe(
-      int(chrome::NOTIFICATION_PREF_INITIALIZATION_COMPLETED),
-      content::Source<PrefService>(&pref_service_),
-      Property(&content::Details<bool>::ptr, testing::Pointee(true))));
+  MockPrefInitObserver observer;
+  notifier.AddInitObserver(
+      base::Bind(&MockPrefInitObserver::OnInitializationCompleted,
+                 base::Unretained(&observer)));
+  EXPECT_CALL(observer, OnInitializationCompleted(true));
   notifier.OnInitializationCompleted(true);
 }
 
@@ -155,13 +170,12 @@ TEST_F(PrefNotifierTest, AddAndRemovePrefObservers) {
 }
 
 TEST_F(PrefNotifierTest, FireObservers) {
-  base::FundamentalValue value_true(true);
-  PrefNotifierImpl notifier(&pref_service_);
+  TestingPrefNotifierImpl notifier(&pref_service_);
   notifier.AddPrefObserver(kChangedPref, &obs1_);
   notifier.AddPrefObserver(kUnchangedPref, &obs1_);
 
-  obs1_.Expect(&pref_service_, kChangedPref, &value_true);
-  EXPECT_CALL(obs2_, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(obs1_, OnPreferenceChanged(&pref_service_, kChangedPref));
+  EXPECT_CALL(obs2_, OnPreferenceChanged(_, _)).Times(0);
   notifier.OnPreferenceChanged(kChangedPref);
   Mock::VerifyAndClearExpectations(&obs1_);
   Mock::VerifyAndClearExpectations(&obs2_);
@@ -169,8 +183,8 @@ TEST_F(PrefNotifierTest, FireObservers) {
   notifier.AddPrefObserver(kChangedPref, &obs2_);
   notifier.AddPrefObserver(kUnchangedPref, &obs2_);
 
-  obs1_.Expect(&pref_service_, kChangedPref, &value_true);
-  obs2_.Expect(&pref_service_, kChangedPref, &value_true);
+  EXPECT_CALL(obs1_, OnPreferenceChanged(&pref_service_, kChangedPref));
+  EXPECT_CALL(obs2_, OnPreferenceChanged(&pref_service_, kChangedPref));
   notifier.OnPreferenceChanged(kChangedPref);
   Mock::VerifyAndClearExpectations(&obs1_);
   Mock::VerifyAndClearExpectations(&obs2_);
@@ -178,8 +192,8 @@ TEST_F(PrefNotifierTest, FireObservers) {
   // Make sure removing an observer from one pref doesn't affect anything else.
   notifier.RemovePrefObserver(kChangedPref, &obs1_);
 
-  EXPECT_CALL(obs1_, Observe(_, _, _)).Times(0);
-  obs2_.Expect(&pref_service_, kChangedPref, &value_true);
+  EXPECT_CALL(obs1_, OnPreferenceChanged(_, _)).Times(0);
+  EXPECT_CALL(obs2_, OnPreferenceChanged(&pref_service_, kChangedPref));
   notifier.OnPreferenceChanged(kChangedPref);
   Mock::VerifyAndClearExpectations(&obs1_);
   Mock::VerifyAndClearExpectations(&obs2_);
@@ -187,8 +201,8 @@ TEST_F(PrefNotifierTest, FireObservers) {
   // Make sure removing an observer entirely doesn't affect anything else.
   notifier.RemovePrefObserver(kUnchangedPref, &obs1_);
 
-  EXPECT_CALL(obs1_, Observe(_, _, _)).Times(0);
-  obs2_.Expect(&pref_service_, kChangedPref, &value_true);
+  EXPECT_CALL(obs1_, OnPreferenceChanged(_, _)).Times(0);
+  EXPECT_CALL(obs2_, OnPreferenceChanged(&pref_service_, kChangedPref));
   notifier.OnPreferenceChanged(kChangedPref);
   Mock::VerifyAndClearExpectations(&obs1_);
   Mock::VerifyAndClearExpectations(&obs2_);
diff --git a/chrome/browser/prefs/pref_observer_mock.cc b/chrome/browser/prefs/pref_observer_mock.cc
index d42c69c..0b3f82ad 100644
--- a/chrome/browser/prefs/pref_observer_mock.cc
+++ b/chrome/browser/prefs/pref_observer_mock.cc
@@ -9,12 +9,9 @@ PrefObserverMock::PrefObserverMock() {}
 
 PrefObserverMock::~PrefObserverMock() {}
 
-void PrefObserverMock::Expect(const PrefService* prefs,
+void PrefObserverMock::Expect(PrefServiceBase* prefs,
                               const std::string& pref_name,
                               const Value* value) {
-  EXPECT_CALL(*this, Observe(int(chrome::NOTIFICATION_PREF_CHANGED),
-                             content::Source<PrefService>(prefs),
-                             Property(&content::Details<std::string>::ptr,
-                                      Pointee(pref_name))))
+  EXPECT_CALL(*this, OnPreferenceChanged(prefs, pref_name))
       .With(PrefValueMatches(prefs, pref_name, value));
 }
diff --git a/chrome/browser/prefs/pref_observer_mock.h b/chrome/browser/prefs/pref_observer_mock.h
index 9697d24..be7f4ff 100644
--- a/chrome/browser/prefs/pref_observer_mock.h
+++ b/chrome/browser/prefs/pref_observer_mock.h
@@ -7,11 +7,8 @@
 
 #include <string>
 
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/prefs/pref_service.h"
-#include "content/public/browser/notification_details.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_source.h"
-#include "content/public/browser/notification_types.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
 using testing::Pointee;
@@ -22,7 +19,7 @@ using testing::Truly;
 // |pref_name| in |prefs| matches |value|. If |value| is NULL, the matcher
 // checks that the value is not set.
 MATCHER_P3(PrefValueMatches, prefs, pref_name, value, "") {
-  const PrefService::Preference* pref =
+  const PrefServiceBase::Preference* pref =
       prefs->FindPreference(pref_name.c_str());
   if (!pref)
     return false;
@@ -36,16 +33,14 @@ MATCHER_P3(PrefValueMatches, prefs, pref_name, value, "") {
 }
 
 // A mock for testing preference notifications and easy setup of expectations.
-class PrefObserverMock : public content::NotificationObserver {
+class PrefObserverMock : public PrefObserver {
  public:
   PrefObserverMock();
   virtual ~PrefObserverMock();
 
-  MOCK_METHOD3(Observe, void(int type,
-                             const content::NotificationSource& source,
-                             const content::NotificationDetails& details));
+  MOCK_METHOD2(OnPreferenceChanged, void(PrefServiceBase*, const std::string&));
 
-  void Expect(const PrefService* prefs,
+  void Expect(PrefServiceBase* prefs,
               const std::string& pref_name,
               const Value* value);
 };
diff --git a/chrome/browser/prefs/pref_service.cc b/chrome/browser/prefs/pref_service.cc
index 36fd093..1eb80b4 100644
--- a/chrome/browser/prefs/pref_service.cc
+++ b/chrome/browser/prefs/pref_service.cc
@@ -769,16 +769,18 @@ const ListValue* PrefService::GetList(const char* path) const {
   return static_cast<const ListValue*>(value);
 }
 
-void PrefService::AddPrefObserver(const char* path,
-                                  content::NotificationObserver* obs) {
+void PrefService::AddPrefObserver(const char* path, PrefObserver* obs) {
   pref_notifier_->AddPrefObserver(path, obs);
 }
 
-void PrefService::RemovePrefObserver(const char* path,
-                                     content::NotificationObserver* obs) {
+void PrefService::RemovePrefObserver(const char* path, PrefObserver* obs) {
   pref_notifier_->RemovePrefObserver(path, obs);
 }
 
+void PrefService::AddPrefInitObserver(base::Callback<void(bool)> obs) {
+  pref_notifier_->AddInitObserver(obs);
+}
+
 void PrefService::RegisterPreference(const char* path,
                                      Value* default_value,
                                      PrefSyncStatus sync_status) {
diff --git a/chrome/browser/prefs/pref_service.h b/chrome/browser/prefs/pref_service.h
index c855ef1..1536b95 100644
--- a/chrome/browser/prefs/pref_service.h
+++ b/chrome/browser/prefs/pref_service.h
@@ -14,6 +14,7 @@
 #include <set>
 #include <string>
 
+#include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/hash_tables.h"
@@ -27,6 +28,7 @@ class PersistentPrefStore;
 class PrefModelAssociator;
 class PrefNotifier;
 class PrefNotifierImpl;
+class PrefObserver;
 class PrefServiceObserver;
 class PrefStore;
 class PrefValueStore;
@@ -277,6 +279,11 @@ class PrefService : public PrefServiceBase, public base::NonThreadSafe {
   // Do not call this after having derived an incognito or per tab pref service.
   void UpdateCommandLinePrefStore(CommandLine* command_line);
 
+  // We run the callback once, when initialization completes. The bool
+  // parameter will be set to true for successful initialization,
+  // false for unsuccessful.
+  void AddPrefInitObserver(base::Callback<void(bool)> callback);
+
  protected:
   // Construct a new pref service. This constructor is what
   // factory methods end up calling and what is used for unit tests.
@@ -306,9 +313,9 @@ class PrefService : public PrefServiceBase, public base::NonThreadSafe {
 
   // PrefServiceBase implementation (protected in base, private here).
   virtual void AddPrefObserver(const char* path,
-                               content::NotificationObserver* obs) OVERRIDE;
+                               PrefObserver* obs) OVERRIDE;
   virtual void RemovePrefObserver(const char* path,
-                                  content::NotificationObserver* obs) OVERRIDE;
+                                  PrefObserver* obs) OVERRIDE;
 
   // Sends notification of a changed preference. This needs to be called by
   // a ScopedUserPrefUpdate if a DictionaryValue or ListValue is changed.
diff --git a/chrome/browser/prefs/pref_service_unittest.cc b/chrome/browser/prefs/pref_service_unittest.cc
index cd046e8..280a346 100644
--- a/chrome/browser/prefs/pref_service_unittest.cc
+++ b/chrome/browser/prefs/pref_service_unittest.cc
@@ -60,7 +60,7 @@ TEST(PrefServiceTest, NoObserverFire) {
 
   // Setting the pref to the same value should not set the pref value a second
   // time.
-  EXPECT_CALL(obs, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(obs, OnPreferenceChanged(_, _)).Times(0);
   prefs.SetString(pref_name, new_pref_value);
   Mock::VerifyAndClearExpectations(&obs);
 
@@ -71,7 +71,7 @@ TEST(PrefServiceTest, NoObserverFire) {
   Mock::VerifyAndClearExpectations(&obs);
 
   // Clearing the pref again should not cause the pref to fire.
-  EXPECT_CALL(obs, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(obs, OnPreferenceChanged(_, _)).Times(0);
   prefs.ClearPref(pref_name);
   Mock::VerifyAndClearExpectations(&obs);
 }
@@ -137,7 +137,7 @@ TEST(PrefServiceTest, Observers) {
 
   // Make sure obs2 still works after removing obs.
   registrar.Remove(pref_name, &obs);
-  EXPECT_CALL(obs, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(obs, OnPreferenceChanged(_, _)).Times(0);
   obs2.Expect(&prefs, pref_name, &expected_new_pref_value);
   // This should only fire the observer in obs2.
   prefs.SetString(pref_name, new_pref_value);
@@ -379,7 +379,7 @@ TEST_F(PrefServiceSetValueTest, SetStringValue) {
   prefs_.Set(kName, default_value);
   Mock::VerifyAndClearExpectations(&observer_);
 
-  EXPECT_CALL(observer_, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(observer_, OnPreferenceChanged(_, _)).Times(0);
   prefs_.Set(kName, default_value);
   Mock::VerifyAndClearExpectations(&observer_);
 
@@ -395,7 +395,7 @@ TEST_F(PrefServiceSetValueTest, SetDictionaryValue) {
   registrar.Init(&prefs_);
   registrar.Add(kName, &observer_);
 
-  EXPECT_CALL(observer_, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(observer_, OnPreferenceChanged(_, _)).Times(0);
   prefs_.RemoveUserPref(kName);
   Mock::VerifyAndClearExpectations(&observer_);
 
@@ -405,7 +405,7 @@ TEST_F(PrefServiceSetValueTest, SetDictionaryValue) {
   prefs_.Set(kName, new_value);
   Mock::VerifyAndClearExpectations(&observer_);
 
-  EXPECT_CALL(observer_, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(observer_, OnPreferenceChanged(_, _)).Times(0);
   prefs_.Set(kName, new_value);
   Mock::VerifyAndClearExpectations(&observer_);
 
@@ -421,7 +421,7 @@ TEST_F(PrefServiceSetValueTest, SetListValue) {
   registrar.Init(&prefs_);
   registrar.Add(kName, &observer_);
 
-  EXPECT_CALL(observer_, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(observer_, OnPreferenceChanged(_, _)).Times(0);
   prefs_.RemoveUserPref(kName);
   Mock::VerifyAndClearExpectations(&observer_);
 
@@ -431,7 +431,7 @@ TEST_F(PrefServiceSetValueTest, SetListValue) {
   prefs_.Set(kName, new_value);
   Mock::VerifyAndClearExpectations(&observer_);
 
-  EXPECT_CALL(observer_, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(observer_, OnPreferenceChanged(_, _)).Times(0);
   prefs_.Set(kName, new_value);
   Mock::VerifyAndClearExpectations(&observer_);
 
diff --git a/chrome/browser/prefs/pref_value_store.h b/chrome/browser/prefs/pref_value_store.h
index 7c34fe1..4c027a5 100644
--- a/chrome/browser/prefs/pref_value_store.h
+++ b/chrome/browser/prefs/pref_value_store.h
@@ -14,7 +14,6 @@
 #include "base/memory/ref_counted.h"
 #include "base/prefs/pref_store.h"
 #include "base/values.h"
-#include "content/public/browser/browser_thread.h"
 
 class PrefModelAssociator;
 class PrefNotifier;
diff --git a/chrome/browser/prefs/scoped_user_pref_update_unittest.cc b/chrome/browser/prefs/scoped_user_pref_update_unittest.cc
index 98ffc89..f5e6927 100644
--- a/chrome/browser/prefs/scoped_user_pref_update_unittest.cc
+++ b/chrome/browser/prefs/scoped_user_pref_update_unittest.cc
@@ -42,7 +42,7 @@ TEST_F(ScopedUserPrefUpdateTest, RegularUse) {
   expected_dictionary.SetString(kKey, kValue);
 
   {
-    EXPECT_CALL(observer_, Observe(_, _, _)).Times(0);
+    EXPECT_CALL(observer_, OnPreferenceChanged(_, _)).Times(0);
     DictionaryPrefUpdate update(&prefs_, kPref);
     DictionaryValue* value = update.Get();
     ASSERT_TRUE(value);
@@ -69,7 +69,7 @@ TEST_F(ScopedUserPrefUpdateTest, RegularUse) {
 
 TEST_F(ScopedUserPrefUpdateTest, NeverTouchAnything) {
   const DictionaryValue* old_value = prefs_.GetDictionary(kPref);
-  EXPECT_CALL(observer_, Observe(_, _, _)).Times(0);
+  EXPECT_CALL(observer_, OnPreferenceChanged(_, _)).Times(0);
   {
     DictionaryPrefUpdate update(&prefs_, kPref);
   }
diff --git a/chrome/browser/printing/cloud_print/cloud_print_proxy_service.cc b/chrome/browser/printing/cloud_print/cloud_print_proxy_service.cc
index 49dadfb..18ed40d 100644
--- a/chrome/browser/printing/cloud_print/cloud_print_proxy_service.cc
+++ b/chrome/browser/printing/cloud_print/cloud_print_proxy_service.cc
@@ -207,11 +207,8 @@ void CloudPrintProxyService::OnCloudPrintSetupClosed() {
       FROM_HERE, base::Bind(&browser::EndKeepAlive));
 }
 
-void CloudPrintProxyService::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
+void CloudPrintProxyService::OnPreferenceChanged(PrefServiceBase* service,
+                                                 const std::string& pref_name) {
   ApplyCloudPrintConnectorPolicy();
 }
 
diff --git a/chrome/browser/printing/cloud_print/cloud_print_proxy_service.h b/chrome/browser/printing/cloud_print/cloud_print_proxy_service.h
index 99bee15..e12a942 100644
--- a/chrome/browser/printing/cloud_print/cloud_print_proxy_service.h
+++ b/chrome/browser/printing/cloud_print/cloud_print_proxy_service.h
@@ -13,9 +13,9 @@
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/printing/cloud_print/cloud_print_setup_handler.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
-#include "content/public/browser/notification_observer.h"
 
 class Profile;
 class ServiceProcessControl;
@@ -29,7 +29,7 @@ struct CloudPrintProxyInfo;
 class CloudPrintProxyService
     : public CloudPrintSetupHandlerDelegate,
       public ProfileKeyedService,
-      public content::NotificationObserver {
+      public PrefObserver {
  public:
   explicit CloudPrintProxyService(Profile* profile);
   virtual ~CloudPrintProxyService();
@@ -63,10 +63,9 @@ class CloudPrintProxyService
   // CloudPrintSetupHandler::Delegate implementation.
   virtual void OnCloudPrintSetupClosed() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   // NotificationDelegate implementation for the token expired notification.
diff --git a/chrome/browser/printing/print_view_manager.cc b/chrome/browser/printing/print_view_manager.cc
index 56c58ca..cad5695 100644
--- a/chrome/browser/printing/print_view_manager.cc
+++ b/chrome/browser/printing/print_view_manager.cc
@@ -389,10 +389,6 @@ void PrintViewManager::Observe(int type,
       OnNotifyPrintJobEvent(*content::Details<JobEventDetails>(details).ptr());
       break;
     }
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      UpdateScriptedPrintingBlocked();
-      break;
-    }
     case chrome::NOTIFICATION_CONTENT_BLOCKED_STATE_CHANGED: {
       tab_content_blocked_ = *content::Details<const bool>(details).ptr();
       UpdateScriptedPrintingBlocked();
@@ -405,6 +401,11 @@ void PrintViewManager::Observe(int type,
   }
 }
 
+void PrintViewManager::OnPreferenceChanged(PrefServiceBase* service,
+                                           const std::string& pref_name) {
+  UpdateScriptedPrintingBlocked();
+}
+
 void PrintViewManager::OnNotifyPrintJobEvent(
     const JobEventDetails& event_details) {
   switch (event_details.type()) {
diff --git a/chrome/browser/printing/print_view_manager.h b/chrome/browser/printing/print_view_manager.h
index e23eaab..d83c1a3 100644
--- a/chrome/browser/printing/print_view_manager.h
+++ b/chrome/browser/printing/print_view_manager.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_PRINTING_PRINT_VIEW_MANAGER_H_
 
 #include "base/memory/ref_counted.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string16.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "content/public/browser/notification_observer.h"
@@ -30,6 +31,7 @@ class PrintViewManagerObserver;
 
 // Manages the print commands for a WebContents.
 class PrintViewManager : public content::NotificationObserver,
+                         public PrefObserver,
                          public PrintedPagesSource,
                          public content::WebContentsObserver,
                          public content::WebContentsUserData<PrintViewManager> {
@@ -77,6 +79,10 @@ class PrintViewManager : public content::NotificationObserver,
   // must be NULL if |observer| is non-NULL.
   void set_observer(PrintViewManagerObserver* observer);
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // PrintedPagesSource implementation.
   virtual string16 RenderSourceName() OVERRIDE;
 
diff --git a/chrome/browser/profiles/gaia_info_update_service.cc b/chrome/browser/profiles/gaia_info_update_service.cc
index efd5188..4d8b4a8 100644
--- a/chrome/browser/profiles/gaia_info_update_service.cc
+++ b/chrome/browser/profiles/gaia_info_update_service.cc
@@ -164,17 +164,10 @@ void GAIAInfoUpdateService::OnProfileDownloadFailure(
   ScheduleNextUpdate();
 }
 
-void GAIAInfoUpdateService::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* name = content::Details<std::string>(details).ptr();
-    if (prefs::kGoogleServicesUsername == *name)
-      OnUsernameChanged();
-  } else {
-    NOTREACHED();
-  }
+void GAIAInfoUpdateService::OnPreferenceChanged(PrefServiceBase* service,
+                                                const std::string& pref_name) {
+  if (prefs::kGoogleServicesUsername == pref_name)
+    OnUsernameChanged();
 }
 
 void GAIAInfoUpdateService::OnUsernameChanged() {
diff --git a/chrome/browser/profiles/gaia_info_update_service.h b/chrome/browser/profiles/gaia_info_update_service.h
index 7129328..bd4ca60 100644
--- a/chrome/browser/profiles/gaia_info_update_service.h
+++ b/chrome/browser/profiles/gaia_info_update_service.h
@@ -8,11 +8,11 @@
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/timer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/profiles/profile_downloader.h"
 #include "chrome/browser/profiles/profile_downloader_delegate.h"
-#include "content/public/browser/notification_observer.h"
 
 class Profile;
 class ProfileDownloader;
@@ -20,7 +20,7 @@ class ProfileDownloader;
 // This service kicks off a download of the user's name and profile picture.
 // The results are saved in the profile info cache.
 class GAIAInfoUpdateService : public ProfileDownloaderDelegate,
-                              public content::NotificationObserver {
+                              public PrefObserver {
  public:
   explicit GAIAInfoUpdateService(Profile* profile);
   virtual ~GAIAInfoUpdateService();
@@ -45,10 +45,9 @@ class GAIAInfoUpdateService : public ProfileDownloaderDelegate,
  private:
   FRIEND_TEST_ALL_PREFIXES(GAIAInfoUpdateServiceTest, ScheduleUpdate);
 
-  // content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
 
   void OnUsernameChanged();
diff --git a/chrome/browser/profiles/off_the_record_profile_impl.h b/chrome/browser/profiles/off_the_record_profile_impl.h
index 799e984..611d9dc 100644
--- a/chrome/browser/profiles/off_the_record_profile_impl.h
+++ b/chrome/browser/profiles/off_the_record_profile_impl.h
@@ -12,6 +12,7 @@
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
 
 using base::Time;
 using base::TimeDelta;
diff --git a/chrome/browser/profiles/profile_impl.cc b/chrome/browser/profiles/profile_impl.cc
index 1d917aa..7902049 100644
--- a/chrome/browser/profiles/profile_impl.cc
+++ b/chrome/browser/profiles/profile_impl.cc
@@ -5,6 +5,7 @@
 #include "chrome/browser/profiles/profile_impl.h"
 
 #include "base/bind.h"
+#include "base/callback.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/environment.h"
@@ -361,10 +362,12 @@ ProfileImpl::ProfileImpl(
         new ExtensionPrefStore(
             ExtensionPrefValueMapFactory::GetForProfile(this), false),
         true));
-    // Wait for the notification that prefs has been loaded (successfully or
-    // not).
-    registrar_.Add(this, chrome::NOTIFICATION_PREF_INITIALIZATION_COMPLETED,
-                   content::Source<PrefService>(prefs_.get()));
+    // Wait for the notification that prefs has been loaded
+    // (successfully or not).  Note that we can use base::Unretained
+    // because the PrefService is owned by this class and lives on
+    // the same thread.
+    prefs_->AddPrefInitObserver(base::Bind(&ProfileImpl::OnPrefsLoaded,
+                                           base::Unretained(this)));
   } else if (create_mode == CREATE_MODE_SYNCHRONOUS) {
     // Load prefs synchronously.
     prefs_.reset(PrefService::CreatePrefService(
@@ -915,32 +918,6 @@ void ProfileImpl::Observe(int type,
                           const content::NotificationSource& source,
                           const content::NotificationDetails& details) {
   switch (type) {
-    case chrome::NOTIFICATION_PREF_INITIALIZATION_COMPLETED: {
-      bool* succeeded = content::Details<bool>(details).ptr();
-      PrefService *prefs = content::Source<PrefService>(source).ptr();
-      DCHECK(prefs == prefs_.get());
-      registrar_.Remove(this,
-                        chrome::NOTIFICATION_PREF_INITIALIZATION_COMPLETED,
-                        content::Source<PrefService>(prefs));
-      OnPrefsLoaded(*succeeded);
-      break;
-    }
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      std::string* pref_name_in = content::Details<std::string>(details).ptr();
-      PrefService* prefs = content::Source<PrefService>(source).ptr();
-      DCHECK(pref_name_in && prefs);
-      if (*pref_name_in == prefs::kGoogleServicesUsername) {
-        UpdateProfileUserNameCache();
-      } else if (*pref_name_in == prefs::kProfileAvatarIndex) {
-        UpdateProfileAvatarCache();
-      } else if (*pref_name_in == prefs::kProfileName) {
-        UpdateProfileNameCache();
-      } else if (*pref_name_in == prefs::kDefaultZoomLevel) {
-          HostZoomMap::GetForBrowserContext(this)->SetDefaultZoomLevel(
-              prefs->GetDouble(prefs::kDefaultZoomLevel));
-      }
-      break;
-    }
     case chrome::NOTIFICATION_BOOKMARK_MODEL_LOADED:
       // Causes lazy-load if sync is enabled.
       ProfileSyncServiceFactory::GetInstance()->GetForProfile(this);
@@ -969,6 +946,21 @@ void ProfileImpl::Observe(int type,
   }
 }
 
+void ProfileImpl::OnPreferenceChanged(PrefServiceBase* prefs,
+                                      const std::string& pref_name_in) {
+  DCHECK(prefs);
+  if (pref_name_in == prefs::kGoogleServicesUsername) {
+    UpdateProfileUserNameCache();
+  } else if (pref_name_in == prefs::kProfileAvatarIndex) {
+    UpdateProfileAvatarCache();
+  } else if (pref_name_in == prefs::kProfileName) {
+    UpdateProfileNameCache();
+  } else if (pref_name_in == prefs::kDefaultZoomLevel) {
+    HostZoomMap::GetForBrowserContext(this)->SetDefaultZoomLevel(
+        prefs->GetDouble(prefs::kDefaultZoomLevel));
+  }
+}
+
 #if defined(ENABLE_SESSION_SERVICE)
 void ProfileImpl::StopCreateSessionServiceTimer() {
   create_session_service_timer_.Stop();
diff --git a/chrome/browser/profiles/profile_impl.h b/chrome/browser/profiles/profile_impl.h
index ad7c17f..36ed8bc 100644
--- a/chrome/browser/profiles/profile_impl.h
+++ b/chrome/browser/profiles/profile_impl.h
@@ -22,6 +22,7 @@
 
 class NetPrefObserver;
 class PrefService;
+class PrefServiceBase;
 class PromoResourceService;
 class SSLConfigServiceManager;
 
@@ -47,7 +48,8 @@ class ExtensionSystem;
 
 // The default profile implementation.
 class ProfileImpl : public Profile,
-                    public content::NotificationObserver {
+                    public content::NotificationObserver,
+                    public PrefObserver {
  public:
   // Value written to prefs when the exit type is EXIT_NORMAL. Public for tests.
   static const char* const kPrefExitTypeNormal;
@@ -131,6 +133,10 @@ class ProfileImpl : public Profile,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
  private:
   friend class Profile;
   FRIEND_TEST_ALL_PREFIXES(StartupBrowserCreatorTest,
@@ -153,6 +159,9 @@ class ProfileImpl : public Profile,
 
   void InitHostZoomMap();
 
+  void OnInitializationCompleted(PrefServiceBase* pref_service,
+                                 bool succeeded);
+
   // Does final prefs initialization and calls Init().
   void OnPrefsLoaded(bool success);
 
diff --git a/chrome/browser/protector/base_prefs_change.cc b/chrome/browser/protector/base_prefs_change.cc
index 2a4a871..9ca25c8 100644
--- a/chrome/browser/protector/base_prefs_change.cc
+++ b/chrome/browser/protector/base_prefs_change.cc
@@ -43,12 +43,9 @@ void BasePrefsChange::IgnorePrefChanges() {
   pref_observer_.RemoveAll();
 }
 
-void BasePrefsChange::Observe(int type,
-                             const content::NotificationSource& source,
-                             const content::NotificationDetails& details) {
-  DCHECK(type == chrome::NOTIFICATION_PREF_CHANGED);
-  const std::string* pref_name = content::Details<std::string>(details).ptr();
-  DCHECK(pref_name && pref_observer_.IsObserved(*pref_name));
+void BasePrefsChange::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
+  DCHECK(pref_observer_.IsObserved(pref_name));
   // Will delete this instance.
   ProtectorServiceFactory::GetForProfile(profile())->DismissChange(this);
 }
diff --git a/chrome/browser/protector/base_prefs_change.h b/chrome/browser/protector/base_prefs_change.h
index 79f5b88..ba29d3a 100644
--- a/chrome/browser/protector/base_prefs_change.h
+++ b/chrome/browser/protector/base_prefs_change.h
@@ -9,14 +9,14 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/protector/base_setting_change.h"
-#include "content/public/browser/notification_observer.h"
 
 namespace protector {
 
 // BaseSettingChange subclass for PrefService-managed settings changes.
 class BasePrefsChange : public BaseSettingChange,
-                        public content::NotificationObserver {
+                        public PrefObserver {
  public:
   BasePrefsChange();
   virtual ~BasePrefsChange();
@@ -35,10 +35,9 @@ class BasePrefsChange : public BaseSettingChange,
   void IgnorePrefChanges();
 
  private:
-  // content::NotificationObserver overrides:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver overrides:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   PrefChangeRegistrar pref_observer_;
 
diff --git a/chrome/browser/protector/protected_prefs_watcher.cc b/chrome/browser/protector/protected_prefs_watcher.cc
index b98438d..ed13224 100644
--- a/chrome/browser/protector/protected_prefs_watcher.cc
+++ b/chrome/browser/protector/protected_prefs_watcher.cc
@@ -195,14 +195,10 @@ void ProtectedPrefsWatcher::ForceUpdateBackup() {
   InitBackup();
 }
 
-void ProtectedPrefsWatcher::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK(type == chrome::NOTIFICATION_PREF_CHANGED);
-  const std::string* pref_name = content::Details<std::string>(details).ptr();
-  DCHECK(pref_name && pref_observer_.IsObserved(*pref_name));
-  if (UpdateBackupEntry(*pref_name))
+void ProtectedPrefsWatcher::OnPreferenceChanged(PrefServiceBase* service,
+                                                const std::string& pref_name) {
+  DCHECK(pref_observer_.IsObserved(pref_name));
+  if (UpdateBackupEntry(pref_name))
     UpdateBackupSignature();
 }
 
diff --git a/chrome/browser/protector/protected_prefs_watcher.h b/chrome/browser/protector/protected_prefs_watcher.h
index 1aaf030..269edc3 100644
--- a/chrome/browser/protector/protected_prefs_watcher.h
+++ b/chrome/browser/protector/protected_prefs_watcher.h
@@ -10,8 +10,8 @@
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/extensions/extension_prefs.h"
-#include "content/public/browser/notification_observer.h"
 
 class PrefService;
 class Profile;
@@ -22,7 +22,7 @@ class Value;
 
 namespace protector {
 
-class ProtectedPrefsWatcher : public content::NotificationObserver {
+class ProtectedPrefsWatcher : public PrefObserver {
  public:
   // Current backup version.
   static const int kCurrentVersionNumber;
@@ -51,10 +51,9 @@ class ProtectedPrefsWatcher : public content::NotificationObserver {
  private:
   friend class ProtectedPrefsWatcherTest;
 
-  // content::NotificationObserver overrides:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver overrides:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Makes sure that all protected prefs have been migrated before starting to
   // observe them.
diff --git a/chrome/browser/safe_browsing/safe_browsing_service.cc b/chrome/browser/safe_browsing/safe_browsing_service.cc
index ab82ddf..6d5456f 100644
--- a/chrome/browser/safe_browsing/safe_browsing_service.cc
+++ b/chrome/browser/safe_browsing/safe_browsing_service.cc
@@ -1369,18 +1369,18 @@ void SafeBrowsingService::Observe(int type,
         RemovePrefService(profile->GetPrefs());
       break;
     }
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-      std::string* pref = content::Details<std::string>(details).ptr();
-      DCHECK(*pref == prefs::kSafeBrowsingEnabled);
-      RefreshState();
-      break;
-    }
     default:
       NOTREACHED();
   }
 }
 
+void SafeBrowsingService::OnPreferenceChanged(PrefServiceBase* service,
+                                              const std::string& pref_name) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(pref_name == prefs::kSafeBrowsingEnabled);
+  RefreshState();
+}
+
 bool SafeBrowsingService::IsWhitelisted(const UnsafeResource& resource) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   // Check if the user has already ignored our warning for this render_view
diff --git a/chrome/browser/safe_browsing/safe_browsing_service.h b/chrome/browser/safe_browsing/safe_browsing_service.h
index d650ae1..bf29fb4 100644
--- a/chrome/browser/safe_browsing/safe_browsing_service.h
+++ b/chrome/browser/safe_browsing/safe_browsing_service.h
@@ -20,6 +20,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/synchronization/lock.h"
 #include "base/time.h"
@@ -55,7 +56,8 @@ class DownloadProtectionService;
 class SafeBrowsingService
     : public base::RefCountedThreadSafe<
           SafeBrowsingService, content::BrowserThread::DeleteOnUIThread>,
-      public content::NotificationObserver {
+      public content::NotificationObserver,
+      public PrefObserver {
  public:
   class Client;
   // Passed a boolean indicating whether or not it is OK to proceed with
@@ -470,6 +472,10 @@ class SafeBrowsingService
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver override
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Starts following the safe browsing preference on |pref_service|.
   void AddPrefService(PrefService* pref_service);
 
diff --git a/chrome/browser/safe_browsing/safe_browsing_tab_observer.cc b/chrome/browser/safe_browsing/safe_browsing_tab_observer.cc
index 60444ae..06d4ca1 100644
--- a/chrome/browser/safe_browsing/safe_browsing_tab_observer.cc
+++ b/chrome/browser/safe_browsing/safe_browsing_tab_observer.cc
@@ -55,26 +55,16 @@ SafeBrowsingTabObserver::~SafeBrowsingTabObserver() {
 ////////////////////////////////////////////////////////////////////////////////
 // content::NotificationObserver overrides
 
-void SafeBrowsingTabObserver::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      Profile* profile =
-          Profile::FromBrowserContext(web_contents_->GetBrowserContext());
-      std::string* pref_name = content::Details<std::string>(details).ptr();
-      DCHECK(content::Source<PrefService>(source).ptr() ==
-             profile->GetPrefs());
-      if (*pref_name == prefs::kSafeBrowsingEnabled) {
-        UpdateSafebrowsingDetectionHost();
-      } else {
-        NOTREACHED() << "unexpected pref change notification" << *pref_name;
-      }
-      break;
-    }
-    default:
-      NOTREACHED();
+void SafeBrowsingTabObserver::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  Profile* profile =
+      Profile::FromBrowserContext(web_contents_->GetBrowserContext());
+  DCHECK(service == profile->GetPrefs());
+  if (pref_name == prefs::kSafeBrowsingEnabled) {
+    UpdateSafebrowsingDetectionHost();
+  } else {
+    NOTREACHED() << "unexpected pref change notification" << pref_name;
   }
 }
 
diff --git a/chrome/browser/safe_browsing/safe_browsing_tab_observer.h b/chrome/browser/safe_browsing/safe_browsing_tab_observer.h
index ec97fee..b41ecb9 100644
--- a/chrome/browser/safe_browsing/safe_browsing_tab_observer.h
+++ b/chrome/browser/safe_browsing/safe_browsing_tab_observer.h
@@ -7,7 +7,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
-#include "content/public/browser/notification_observer.h"
+#include "base/prefs/public/pref_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace content {
@@ -20,7 +20,7 @@ class ClientSideDetectionHost;
 
 // Per-tab class to handle safe-browsing functionality.
 class SafeBrowsingTabObserver
-    : public content::NotificationObserver,
+    : public PrefObserver,
       public content::WebContentsUserData<SafeBrowsingTabObserver> {
  public:
   virtual ~SafeBrowsingTabObserver();
@@ -29,10 +29,9 @@ class SafeBrowsingTabObserver
   explicit SafeBrowsingTabObserver(content::WebContents* web_contents);
   friend class content::WebContentsUserData<SafeBrowsingTabObserver>;
 
-  // content::NotificationObserver overrides:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver overrides:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Internal helpers ----------------------------------------------------------
 
diff --git a/chrome/browser/search_engines/template_url_service.cc b/chrome/browser/search_engines/template_url_service.cc
index c8d3e01..e4c250e 100644
--- a/chrome/browser/search_engines/template_url_service.cc
+++ b/chrome/browser/search_engines/template_url_service.cc
@@ -921,32 +921,34 @@ void TemplateURLService::Observe(int type,
       GoogleBaseURLChanged(
           content::Details<GoogleURLTracker::UpdatedDetails>(details)->first);
     }
-  } else if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    // Listen for changes to the default search from Sync.
-    DCHECK_EQ(std::string(prefs::kSyncedDefaultSearchProviderGUID),
-              *content::Details<std::string>(details).ptr());
-    PrefService* prefs = GetPrefs();
-    TemplateURL* new_default_search = GetTemplateURLForGUID(
-        prefs->GetString(prefs::kSyncedDefaultSearchProviderGUID));
-    if (new_default_search && !is_default_search_managed_) {
-      if (new_default_search != GetDefaultSearchProvider()) {
-        AutoReset<DefaultSearchChangeOrigin> change_origin(
-            &dsp_change_origin_, DSP_CHANGE_SYNC_PREF);
-        SetDefaultSearchProvider(new_default_search);
-        pending_synced_default_search_ = false;
-      }
-    } else {
-      // If it's not there, or if default search is currently managed, set a
-      // flag to indicate that we waiting on the search engine entry to come
-      // in through Sync.
-      pending_synced_default_search_ = true;
-    }
-    UpdateDefaultSearch();
   } else {
     NOTREACHED();
   }
 }
 
+void TemplateURLService::OnPreferenceChanged(PrefServiceBase* service,
+                                             const std::string& pref_name) {
+  // Listen for changes to the default search from Sync.
+  DCHECK_EQ(std::string(prefs::kSyncedDefaultSearchProviderGUID), pref_name);
+  PrefService* prefs = GetPrefs();
+  TemplateURL* new_default_search = GetTemplateURLForGUID(
+      prefs->GetString(prefs::kSyncedDefaultSearchProviderGUID));
+  if (new_default_search && !is_default_search_managed_) {
+    if (new_default_search != GetDefaultSearchProvider()) {
+      AutoReset<DefaultSearchChangeOrigin> change_origin(
+          &dsp_change_origin_, DSP_CHANGE_SYNC_PREF);
+      SetDefaultSearchProvider(new_default_search);
+      pending_synced_default_search_ = false;
+    }
+  } else {
+    // If it's not there, or if default search is currently managed, set a
+    // flag to indicate that we waiting on the search engine entry to come
+    // in through Sync.
+    pending_synced_default_search_ = true;
+  }
+  UpdateDefaultSearch();
+}
+
 syncer::SyncDataList TemplateURLService::GetAllSyncData(
     syncer::ModelType type) const {
   DCHECK_EQ(syncer::SEARCH_ENGINES, type);
diff --git a/chrome/browser/search_engines/template_url_service.h b/chrome/browser/search_engines/template_url_service.h
index bc62ff5..510f11c 100644
--- a/chrome/browser/search_engines/template_url_service.h
+++ b/chrome/browser/search_engines/template_url_service.h
@@ -15,6 +15,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "chrome/browser/search_engines/template_url_id.h"
 #include "chrome/browser/webdata/web_data_service.h"
@@ -67,6 +68,7 @@ struct URLVisitedDetails;
 class TemplateURLService : public WebDataServiceConsumer,
                            public ProfileKeyedService,
                            public content::NotificationObserver,
+                           public PrefObserver,
                            public syncer::SyncableService {
  public:
   typedef std::map<std::string, std::string> QueryTerms;
@@ -260,10 +262,15 @@ class TemplateURLService : public WebDataServiceConsumer,
   string16 GetKeywordShortName(const string16& keyword,
                                bool* is_extension_keyword);
 
+  // content::NotificationObserver implementation.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // syncer::SyncableService implementation.
 
   // Returns all syncable TemplateURLs from this model as SyncData. This should
diff --git a/chrome/browser/signin/signin_manager.cc b/chrome/browser/signin/signin_manager.cc
index cbf1cd9..56addb0 100644
--- a/chrome/browser/signin/signin_manager.cc
+++ b/chrome/browser/signin/signin_manager.cc
@@ -506,17 +506,6 @@ void SigninManager::Observe(int type,
                             const content::NotificationSource& source,
                             const content::NotificationDetails& details) {
   switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED:
-      DCHECK(*content::Details<std::string>(details).ptr() ==
-             prefs::kGoogleServicesUsernamePattern);
-      if (!authenticated_username_.empty() &&
-          !IsAllowedUsername(authenticated_username_)) {
-        // Signed in user is invalid according to the current policy so sign
-        // the user out.
-        SignOut();
-      }
-      break;
-
 #if !defined(OS_CHROMEOS)
     case chrome::NOTIFICATION_TOKEN_AVAILABLE: {
       TokenService::TokenAvailableDetails* tok_details =
@@ -546,3 +535,13 @@ void SigninManager::Observe(int type,
   }
 }
 
+void SigninManager::OnPreferenceChanged(PrefServiceBase* service,
+                                        const std::string& pref_name) {
+  DCHECK_EQ(std::string(prefs::kGoogleServicesUsernamePattern), pref_name);
+  if (!authenticated_username_.empty() &&
+      !IsAllowedUsername(authenticated_username_)) {
+    // Signed in user is invalid according to the current policy so sign
+    // the user out.
+    SignOut();
+  }
+}
diff --git a/chrome/browser/signin/signin_manager.h b/chrome/browser/signin/signin_manager.h
index ce616eb..d63df0c 100644
--- a/chrome/browser/signin/signin_manager.h
+++ b/chrome/browser/signin/signin_manager.h
@@ -24,6 +24,7 @@
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -49,6 +50,7 @@ struct GoogleServiceSigninSuccessDetails {
 
 class SigninManager : public GaiaAuthConsumer,
                       public content::NotificationObserver,
+                      public PrefObserver,
                       public ProfileKeyedService {
  public:
   // Returns true if the cookie policy for the given profile allows cookies
@@ -146,6 +148,10 @@ class SigninManager : public GaiaAuthConsumer,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
  protected:
   // Weak pointer to parent profile (protected so FakeSigninManager can access
   // it).
diff --git a/chrome/browser/speech/chrome_speech_recognition_preferences.cc b/chrome/browser/speech/chrome_speech_recognition_preferences.cc
index f5ef511..fc057fe 100644
--- a/chrome/browser/speech/chrome_speech_recognition_preferences.cc
+++ b/chrome/browser/speech/chrome_speech_recognition_preferences.cc
@@ -141,14 +141,11 @@ void ChromeSpeechRecognitionPreferences::DetachFromProfile() {
   profile_ = NULL;
 }
 
-void ChromeSpeechRecognitionPreferences::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void ChromeSpeechRecognitionPreferences::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK_EQ(type, chrome::NOTIFICATION_PREF_CHANGED);
-  std::string* pref_name = content::Details<std::string>(details).ptr();
-  ReloadPreference(*pref_name);
+  ReloadPreference(pref_name);
 }
 
 bool ChromeSpeechRecognitionPreferences::FilterProfanities() const {
diff --git a/chrome/browser/speech/chrome_speech_recognition_preferences.h b/chrome/browser/speech/chrome_speech_recognition_preferences.h
index 5090ea3..6bab299 100644
--- a/chrome/browser/speech/chrome_speech_recognition_preferences.h
+++ b/chrome/browser/speech/chrome_speech_recognition_preferences.h
@@ -10,11 +10,11 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/non_thread_safe.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "chrome/browser/profiles/profile_keyed_service_factory.h"
-#include "content/public/browser/notification_observer.h"
 #include "content/public/browser/speech_recognition_preferences.h"
 
 class PrefService;
@@ -34,16 +34,15 @@ class ListValue;
 
 class ChromeSpeechRecognitionPreferences
     : public content::SpeechRecognitionPreferences,
-      public content::NotificationObserver {
+      public PrefObserver {
  public:
   static void InitializeFactory();
   static scoped_refptr<ChromeSpeechRecognitionPreferences> GetForProfile(
       Profile* profile);
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
 
   // content::SpeechRecognitionPreferences implementation.
diff --git a/chrome/browser/spellchecker/spellcheck_profile.cc b/chrome/browser/spellchecker/spellcheck_profile.cc
index 09375c5..256251a 100644
--- a/chrome/browser/spellchecker/spellcheck_profile.cc
+++ b/chrome/browser/spellchecker/spellcheck_profile.cc
@@ -112,26 +112,19 @@ void SpellCheckProfile::Shutdown() {
   profile_ = NULL;
 }
 
-void SpellCheckProfile::Observe(int type,
-                                const content::NotificationSource& source,
-                                const content::NotificationDetails& details) {
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      std::string* pref_name_in = content::Details<std::string>(details).ptr();
-      PrefService* prefs = content::Source<PrefService>(source).ptr();
-      DCHECK(pref_name_in && prefs);
-      if (*pref_name_in == prefs::kSpellCheckDictionary ||
-          *pref_name_in == prefs::kEnableSpellCheck) {
-        ReinitializeSpellCheckHost(true);
-      } else if (*pref_name_in == prefs::kEnableAutoSpellCorrect) {
-        bool enabled = prefs->GetBoolean(prefs::kEnableAutoSpellCorrect);
-        for (content::RenderProcessHost::iterator i(
-                content::RenderProcessHost::AllHostsIterator());
-             !i.IsAtEnd(); i.Advance()) {
-          content::RenderProcessHost* process = i.GetCurrentValue();
-          process->Send(new SpellCheckMsg_EnableAutoSpellCorrect(enabled));
-        }
-      }
+void SpellCheckProfile::OnPreferenceChanged(PrefServiceBase* prefs,
+                                            const std::string& pref_name_in) {
+  DCHECK(prefs);
+  if (pref_name_in == prefs::kSpellCheckDictionary ||
+      pref_name_in == prefs::kEnableSpellCheck) {
+    ReinitializeSpellCheckHost(true);
+  } else if (pref_name_in == prefs::kEnableAutoSpellCorrect) {
+    bool enabled = prefs->GetBoolean(prefs::kEnableAutoSpellCorrect);
+    for (content::RenderProcessHost::iterator i(
+             content::RenderProcessHost::AllHostsIterator());
+         !i.IsAtEnd(); i.Advance()) {
+      content::RenderProcessHost* process = i.GetCurrentValue();
+      process->Send(new SpellCheckMsg_EnableAutoSpellCorrect(enabled));
     }
   }
 }
diff --git a/chrome/browser/spellchecker/spellcheck_profile.h b/chrome/browser/spellchecker/spellcheck_profile.h
index a269c6f..7955057 100644
--- a/chrome/browser/spellchecker/spellcheck_profile.h
+++ b/chrome/browser/spellchecker/spellcheck_profile.h
@@ -14,11 +14,11 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "chrome/browser/spellchecker/spellcheck_profile_provider.h"
 #include "chrome/browser/spellchecker/spellcheck_custom_dictionary.h"
 #include "chrome/common/spellcheck_common.h"
-#include "content/public/browser/notification_observer.h"
 
 class Profile;
 class SpellCheckHost;
@@ -38,7 +38,7 @@ class URLRequestContextGetter;
 // can be retrieved from SpellCheckFactory::GetHostForProfile();
 class SpellCheckProfile : public SpellCheckProfileProvider,
                           public ProfileKeyedService,
-                          public content::NotificationObserver {
+                          public PrefObserver {
  public:
   explicit SpellCheckProfile(Profile* profile);
   virtual ~SpellCheckProfile();
@@ -71,10 +71,9 @@ class SpellCheckProfile : public SpellCheckProfileProvider,
   // ProfileKeyedService implementation.
   virtual void Shutdown() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  protected:
   // Only tests should override this.
diff --git a/chrome/browser/sync/credential_cache_service_win.cc b/chrome/browser/sync/credential_cache_service_win.cc
index 9c938d0..8d05e0d 100644
--- a/chrome/browser/sync/credential_cache_service_win.cc
+++ b/chrome/browser/sync/credential_cache_service_win.cc
@@ -94,24 +94,6 @@ void CredentialCacheService::Observe(
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(local_store_.get());
   switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      // One of the two sync encryption tokens has changed. Update its value in
-      // the local cache.
-      const std::string pref_name =
-          *(content::Details<const std::string>(details).ptr());
-      if (pref_name == prefs::kSyncEncryptionBootstrapToken) {
-        PackAndUpdateStringPref(pref_name,
-                                sync_prefs_.GetEncryptionBootstrapToken());
-      } else if (pref_name == prefs::kSyncKeystoreEncryptionBootstrapToken) {
-        PackAndUpdateStringPref(
-            pref_name,
-            sync_prefs_.GetKeystoreEncryptionBootstrapToken());
-      } else {
-        NOTREACHED() "Invalid pref name " << pref_name << ".";
-      }
-      break;
-    }
-
     case chrome::NOTIFICATION_GOOGLE_SIGNED_OUT: {
       // The user has signed out. Write blank values to the google username,
       // encryption tokens and token service credentials in the local cache.
@@ -193,6 +175,22 @@ void CredentialCacheService::Observe(
   }
 }
 
+void CredentialCacheService::OnPreferenceChanged(PrefServiceBase* service,
+                                                 const std::string& pref_name) {
+  // One of the two sync encryption tokens has changed. Update its value in
+  // the local cache.
+  if (pref_name == prefs::kSyncEncryptionBootstrapToken) {
+    PackAndUpdateStringPref(pref_name,
+                            sync_prefs_.GetEncryptionBootstrapToken());
+  } else if (pref_name == prefs::kSyncKeystoreEncryptionBootstrapToken) {
+    PackAndUpdateStringPref(
+        pref_name,
+        sync_prefs_.GetKeystoreEncryptionBootstrapToken());
+  } else {
+    NOTREACHED() "Invalid pref name " << pref_name << ".";
+  }
+}
+
 void CredentialCacheService::ReadCachedCredentialsFromAlternateProfile() {
   // If the local user has signed in and signed out, we do not consume cached
   // credentials from the alternate profile. There is nothing more to do, now or
diff --git a/chrome/browser/sync/credential_cache_service_win.h b/chrome/browser/sync/credential_cache_service_win.h
index 625f608..1aea150 100644
--- a/chrome/browser/sync/credential_cache_service_win.h
+++ b/chrome/browser/sync/credential_cache_service_win.h
@@ -14,6 +14,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/json_pref_store.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "chrome/browser/sync/sync_prefs.h"
 #include "content/public/browser/notification_observer.h"
@@ -39,7 +40,8 @@ namespace syncer {
 // sync using credentials that were cached due to signing in on the other
 // (alternate) mode.
 class CredentialCacheService : public ProfileKeyedService,
-                               public content::NotificationObserver {
+                               public content::NotificationObserver,
+                               public PrefObserver {
  public:
   explicit CredentialCacheService(Profile* profile);
   virtual ~CredentialCacheService();
@@ -52,6 +54,10 @@ class CredentialCacheService : public ProfileKeyedService,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Loads cached sync credentials from the alternate profile and applies them
   // to the local profile if the load was successful.
   void ReadCachedCredentialsFromAlternateProfile();
diff --git a/chrome/browser/sync/glue/typed_url_data_type_controller.cc b/chrome/browser/sync/glue/typed_url_data_type_controller.cc
index 88a9d23..0e9713f 100644
--- a/chrome/browser/sync/glue/typed_url_data_type_controller.cc
+++ b/chrome/browser/sync/glue/typed_url_data_type_controller.cc
@@ -87,29 +87,22 @@ void TypedUrlDataTypeController::SetBackend(history::HistoryBackend* backend) {
   backend_ = backend;
 }
 
-void TypedUrlDataTypeController::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void TypedUrlDataTypeController::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED:
-      DCHECK(*content::Details<std::string>(details).ptr() ==
-             prefs::kSavingBrowserHistoryDisabled);
-      if (profile()->GetPrefs()->GetBoolean(
-              prefs::kSavingBrowserHistoryDisabled)) {
-        // We've turned off history persistence, so if we are running,
-        // generate an unrecoverable error. This can be fixed by restarting
-        // Chrome (on restart, typed urls will not be a registered type).
-        if (state() != NOT_RUNNING && state() != STOPPING) {
-          profile_sync_service()->DisableBrokenDatatype(syncer::TYPED_URLS,
-              FROM_HERE, "History saving is now disabled by policy.");
-        }
-      }
-      break;
-    default:
-      NOTREACHED();
-      break;
+  DCHECK_EQ(std::string(prefs::kSavingBrowserHistoryDisabled), pref_name);
+  if (profile()->GetPrefs()->GetBoolean(
+          prefs::kSavingBrowserHistoryDisabled)) {
+    // We've turned off history persistence, so if we are running,
+    // generate an unrecoverable error. This can be fixed by restarting
+    // Chrome (on restart, typed urls will not be a registered type).
+    if (state() != NOT_RUNNING && state() != STOPPING) {
+      profile_sync_service()->DisableBrokenDatatype(
+          syncer::TYPED_URLS,
+          FROM_HERE,
+          "History saving is now disabled by policy.");
+    }
   }
 }
 
@@ -147,7 +140,6 @@ void TypedUrlDataTypeController::StopModels() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(state() == STOPPING || state() == NOT_RUNNING || state() == DISABLED);
   DVLOG(1) << "TypedUrlDataTypeController::StopModels(): State = " << state();
-  notification_registrar_.RemoveAll();
 }
 
 TypedUrlDataTypeController::~TypedUrlDataTypeController() {}
diff --git a/chrome/browser/sync/glue/typed_url_data_type_controller.h b/chrome/browser/sync/glue/typed_url_data_type_controller.h
index 650152a..e107627 100644
--- a/chrome/browser/sync/glue/typed_url_data_type_controller.h
+++ b/chrome/browser/sync/glue/typed_url_data_type_controller.h
@@ -10,11 +10,9 @@
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/common/cancelable_request.h"
 #include "chrome/browser/sync/glue/non_frontend_data_type_controller.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
-#include "content/public/browser/notification_types.h"
 
 class HistoryService;
 
@@ -28,7 +26,7 @@ class ControlTask;
 
 // A class that manages the startup and shutdown of typed_url sync.
 class TypedUrlDataTypeController : public NonFrontendDataTypeController,
-                                   public content::NotificationObserver {
+                                   public PrefObserver {
  public:
   TypedUrlDataTypeController(
       ProfileSyncComponentsFactory* profile_sync_factory,
@@ -39,10 +37,9 @@ class TypedUrlDataTypeController : public NonFrontendDataTypeController,
   virtual syncer::ModelType type() const OVERRIDE;
   virtual syncer::ModelSafeGroup model_safe_group() const OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Invoked on the history thread to set our history backend - must be called
   // before CreateSyncComponents() is invoked.
@@ -60,7 +57,6 @@ class TypedUrlDataTypeController : public NonFrontendDataTypeController,
   virtual ~TypedUrlDataTypeController();
 
   history::HistoryBackend* backend_;
-  content::NotificationRegistrar notification_registrar_;
   PrefChangeRegistrar pref_registrar_;
 
   // Helper object to make sure we don't leave tasks running on the history
diff --git a/chrome/browser/sync/sync_prefs.cc b/chrome/browser/sync/sync_prefs.cc
index ee9380c..c483966 100644
--- a/chrome/browser/sync/sync_prefs.cc
+++ b/chrome/browser/sync/sync_prefs.cc
@@ -263,24 +263,13 @@ void SyncPrefs::AcknowledgeSyncedTypes(syncer::ModelTypeSet types) {
   pref_service_->Set(prefs::kSyncAcknowledgedSyncTypes, *value);
 }
 
-void SyncPrefs::Observe(int type,
-                        const content::NotificationSource& source,
-                        const content::NotificationDetails& details) {
+void SyncPrefs::OnPreferenceChanged(PrefServiceBase* service,
+                                    const std::string& pref_name) {
   DCHECK(CalledOnValidThread());
-  DCHECK(content::Source<PrefService>(pref_service_) == source);
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      const std::string* pref_name =
-          content::Details<const std::string>(details).ptr();
-      if (*pref_name == prefs::kSyncManaged) {
-        FOR_EACH_OBSERVER(SyncPrefObserver, sync_pref_observers_,
-                          OnSyncManagedPrefChange(*pref_sync_managed_));
-      }
-      break;
-    }
-    default:
-      NOTREACHED();
-      break;
+  DCHECK_EQ(pref_service_, service);
+  if (pref_name == prefs::kSyncManaged) {
+    FOR_EACH_OBSERVER(SyncPrefObserver, sync_pref_observers_,
+                      OnSyncManagedPrefChange(*pref_sync_managed_));
   }
 }
 
diff --git a/chrome/browser/sync/sync_prefs.h b/chrome/browser/sync/sync_prefs.h
index 0786b90..dcb3dbb 100644
--- a/chrome/browser/sync/sync_prefs.h
+++ b/chrome/browser/sync/sync_prefs.h
@@ -9,10 +9,10 @@
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/threading/non_thread_safe.h"
 #include "base/time.h"
 #include "chrome/browser/api/prefs/pref_member.h"
-#include "content/public/browser/notification_observer.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/notifier/invalidation_state_tracker.h"
 
@@ -45,7 +45,7 @@ class SyncPrefObserver {
 //   two_client_preferences_sync_test.cc
 class SyncPrefs : NON_EXPORTED_BASE(public base::NonThreadSafe),
                   public base::SupportsWeakPtr<SyncPrefs>,
-                  public content::NotificationObserver {
+                  public PrefObserver {
  public:
   // |pref_service| may be NULL (for unit tests), but in that case no
   // setter methods should be called.  Does not take ownership of
@@ -116,10 +116,9 @@ class SyncPrefs : NON_EXPORTED_BASE(public base::NonThreadSafe),
   // Merges the given set of types with the set of acknowledged types.
   void AcknowledgeSyncedTypes(syncer::ModelTypeSet types);
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // For testing.
 
diff --git a/chrome/browser/translate/translate_manager.cc b/chrome/browser/translate/translate_manager.cc
index b3bdca7..641b64c 100644
--- a/chrome/browser/translate/translate_manager.cc
+++ b/chrome/browser/translate/translate_manager.cc
@@ -409,18 +409,17 @@ void TranslateManager::Observe(int type,
       delete pref_change_registrar;
       break;
     }
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      DCHECK(*content::Details<std::string>(details).ptr() ==
-             prefs::kAcceptLanguages);
-      PrefService* prefs = content::Source<PrefService>(source).ptr();
-      InitAcceptLanguages(prefs);
-      break;
-    }
     default:
       NOTREACHED();
   }
 }
 
+void TranslateManager::OnPreferenceChanged(PrefServiceBase* service,
+                                           const std::string& pref_name) {
+  DCHECK_EQ(std::string(prefs::kAcceptLanguages), pref_name);
+  InitAcceptLanguages(service);
+}
+
 void TranslateManager::OnURLFetchComplete(const net::URLFetcher* source) {
   if (translate_script_request_pending_.get() != source &&
       language_list_request_pending_.get() != source) {
@@ -789,7 +788,7 @@ bool TranslateManager::IsAcceptLanguage(WebContents* web_contents,
   return iter->second.count(language) != 0;
 }
 
-void TranslateManager::InitAcceptLanguages(PrefService* prefs) {
+void TranslateManager::InitAcceptLanguages(PrefServiceBase* prefs) {
   // We have been asked for this profile, build the languages.
   std::string accept_langs_str = prefs->GetString(prefs::kAcceptLanguages);
   std::vector<std::string> accept_langs_list;
diff --git a/chrome/browser/translate/translate_manager.h b/chrome/browser/translate/translate_manager.h
index 93eca3a..a94a7be 100644
--- a/chrome/browser/translate/translate_manager.h
+++ b/chrome/browser/translate/translate_manager.h
@@ -15,6 +15,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/time.h"
 #include "chrome/common/translate_errors.h"
 #include "content/public/browser/notification_observer.h"
@@ -25,6 +26,7 @@ template <typename T> struct DefaultSingletonTraits;
 class GURL;
 struct PageTranslatedDetails;
 class PrefService;
+class PrefServiceBase;
 class TranslateInfoBarDelegate;
 
 namespace content {
@@ -41,6 +43,7 @@ class URLFetcher;
 // It is a singleton.
 
 class TranslateManager : public content::NotificationObserver,
+                         public PrefObserver,
                          public net::URLFetcherDelegate {
  public:
   // Returns the singleton instance.
@@ -82,6 +85,10 @@ class TranslateManager : public content::NotificationObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // net::URLFetcherDelegate implementation:
   virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE;
 
@@ -167,7 +174,7 @@ class TranslateManager : public content::NotificationObserver,
 
   // Initializes the |accept_languages_| language table based on the associated
   // preference in |prefs|.
-  void InitAcceptLanguages(PrefService* prefs);
+  void InitAcceptLanguages(PrefServiceBase* prefs);
 
   // Fetches the JS translate script (the script that is injected in the page
   // to translate it).
@@ -199,7 +206,7 @@ class TranslateManager : public content::NotificationObserver,
 
   // A map that associates a profile with its parsed "accept languages".
   typedef std::set<std::string> LanguageSet;
-  typedef std::map<PrefService*, LanguageSet> PrefServiceLanguagesMap;
+  typedef std::map<PrefServiceBase*, LanguageSet> PrefServiceLanguagesMap;
   PrefServiceLanguagesMap accept_languages_;
 
   base::WeakPtrFactory<TranslateManager> weak_method_factory_;
diff --git a/chrome/browser/translate/translate_manager_browsertest.cc b/chrome/browser/translate/translate_manager_browsertest.cc
index 30cd55b..e5d26d9 100644
--- a/chrome/browser/translate/translate_manager_browsertest.cc
+++ b/chrome/browser/translate/translate_manager_browsertest.cc
@@ -10,6 +10,7 @@
 #include "base/json/json_writer.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/stringprintf.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
@@ -92,7 +93,8 @@ class NavEntryCommittedObserver : public content::NotificationObserver {
 };
 
 class TranslateManagerTest : public ChromeRenderViewHostTestHarness,
-                             public content::NotificationObserver {
+                             public content::NotificationObserver,
+                             public PrefObserver {
  public:
   TranslateManagerTest()
       : ui_thread_(BrowserThread::UI, &message_loop_) {
@@ -214,6 +216,8 @@ class TranslateManagerTest : public ChromeRenderViewHostTestHarness,
         content::Details<InfoBarRemovedDetails>(details)->first);
   }
 
+  MOCK_METHOD2(OnPreferenceChanged, void(PrefServiceBase*, const std::string&));
+
  protected:
   virtual void SetUp() {
     WebKit::initialize(webkit_platform_support_.Get());
@@ -291,15 +295,9 @@ class TranslateManagerTest : public ChromeRenderViewHostTestHarness,
   }
 
   void SetPrefObserverExpectation(const char* path) {
-    EXPECT_CALL(
-        pref_observer_,
-        Observe(int(chrome::NOTIFICATION_PREF_CHANGED),
-                _,
-                Property(&content::Details<std::string>::ptr, Pointee(path))));
+    EXPECT_CALL(*this, OnPreferenceChanged(_, std::string(path)));
   }
 
-  content::MockNotificationObserver pref_observer_;
-
  private:
   content::NotificationRegistrar notification_registrar_;
   net::TestURLFetcherFactory url_fetcher_factory_;
@@ -1094,8 +1092,7 @@ TEST_F(TranslateManagerTest, NeverTranslateLanguagePref) {
   PrefService* prefs = profile->GetPrefs();
   PrefChangeRegistrar registrar;
   registrar.Init(prefs);
-  registrar.Add(TranslatePrefs::kPrefTranslateLanguageBlacklist,
-                &pref_observer_);
+  registrar.Add(TranslatePrefs::kPrefTranslateLanguageBlacklist, this);
   TranslatePrefs translate_prefs(prefs);
   EXPECT_FALSE(translate_prefs.IsLanguageBlacklisted("fr"));
   EXPECT_TRUE(translate_prefs.CanTranslate(prefs, "fr", url));
@@ -1142,8 +1139,7 @@ TEST_F(TranslateManagerTest, NeverTranslateSitePref) {
   PrefService* prefs = profile->GetPrefs();
   PrefChangeRegistrar registrar;
   registrar.Init(prefs);
-  registrar.Add(TranslatePrefs::kPrefTranslateSiteBlacklist,
-                &pref_observer_);
+  registrar.Add(TranslatePrefs::kPrefTranslateSiteBlacklist, this);
   TranslatePrefs translate_prefs(prefs);
   EXPECT_FALSE(translate_prefs.IsSiteBlacklisted(host));
   EXPECT_TRUE(translate_prefs.CanTranslate(prefs, "fr", url));
@@ -1182,8 +1178,7 @@ TEST_F(TranslateManagerTest, AlwaysTranslateLanguagePref) {
   PrefService* prefs = profile->GetPrefs();
   PrefChangeRegistrar registrar;
   registrar.Init(prefs);
-  registrar.Add(TranslatePrefs::kPrefTranslateWhitelists,
-                &pref_observer_);
+  registrar.Add(TranslatePrefs::kPrefTranslateWhitelists, this);
   TranslatePrefs translate_prefs(prefs);
   SetPrefObserverExpectation(TranslatePrefs::kPrefTranslateWhitelists);
   translate_prefs.WhitelistLanguagePair("fr", "en");
diff --git a/chrome/browser/ui/alternate_error_tab_observer.cc b/chrome/browser/ui/alternate_error_tab_observer.cc
index 73347f4..569a739 100644
--- a/chrome/browser/ui/alternate_error_tab_observer.cc
+++ b/chrome/browser/ui/alternate_error_tab_observer.cc
@@ -56,13 +56,18 @@ void AlternateErrorPageTabObserver::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    DCHECK_EQ(profile_->GetPrefs(), content::Source<PrefService>(source).ptr());
-    DCHECK_EQ(std::string(prefs::kAlternateErrorPagesEnabled),
-              *content::Details<std::string>(details).ptr());
-  } else {
-    DCHECK_EQ(chrome::NOTIFICATION_GOOGLE_URL_UPDATED, type);
-  }
+  DCHECK_EQ(chrome::NOTIFICATION_GOOGLE_URL_UPDATED, type);
+  UpdateAlternateErrorPageURL(web_contents()->GetRenderViewHost());
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// PrefObserver overrides
+
+void AlternateErrorPageTabObserver::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  DCHECK_EQ(profile_->GetPrefs(), service);
+  DCHECK(prefs::kAlternateErrorPagesEnabled == pref_name);
   UpdateAlternateErrorPageURL(web_contents()->GetRenderViewHost());
 }
 
diff --git a/chrome/browser/ui/alternate_error_tab_observer.h b/chrome/browser/ui/alternate_error_tab_observer.h
index d5da940..071dea8 100644
--- a/chrome/browser/ui/alternate_error_tab_observer.h
+++ b/chrome/browser/ui/alternate_error_tab_observer.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_UI_ALTERNATE_ERROR_TAB_OBSERVER_H_
 
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -18,7 +19,8 @@ class Profile;
 class AlternateErrorPageTabObserver
     : public content::WebContentsObserver,
       public content::NotificationObserver,
-      public content::WebContentsUserData<AlternateErrorPageTabObserver> {
+      public content::WebContentsUserData<AlternateErrorPageTabObserver>,
+      public PrefObserver {
  public:
   virtual ~AlternateErrorPageTabObserver();
 
@@ -37,6 +39,10 @@ class AlternateErrorPageTabObserver
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver overrides:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Internal helpers ----------------------------------------------------------
 
   // Returns the server that can provide alternate error pages.  If the returned
diff --git a/chrome/browser/ui/app_list/apps_model_builder.cc b/chrome/browser/ui/app_list/apps_model_builder.cc
index 9eb65a2..8dba307 100644
--- a/chrome/browser/ui/app_list/apps_model_builder.cc
+++ b/chrome/browser/ui/app_list/apps_model_builder.cc
@@ -208,15 +208,16 @@ void AppsModelBuilder::Observe(int type,
       HighlightApp();
       break;
     }
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      ResortApps();
-      break;
-    }
     default:
       NOTREACHED();
   }
 }
 
+void AppsModelBuilder::OnPreferenceChanged(PrefServiceBase* service,
+                                           const std::string& pref_name) {
+  ResortApps();
+}
+
 void AppsModelBuilder::ListItemsAdded(size_t start, size_t count) {
 }
 
diff --git a/chrome/browser/ui/app_list/apps_model_builder.h b/chrome/browser/ui/app_list/apps_model_builder.h
index 5c91583..b943a9a 100644
--- a/chrome/browser/ui/app_list/apps_model_builder.h
+++ b/chrome/browser/ui/app_list/apps_model_builder.h
@@ -9,6 +9,7 @@
 
 #include "base/gtest_prod_util.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ui/app_list/app_list_model.h"
@@ -19,6 +20,7 @@ class ExtensionAppItem;
 class Profile;
 
 class AppsModelBuilder : public content::NotificationObserver,
+                         public PrefObserver,
                          public ui::ListModelObserver {
  public:
   AppsModelBuilder(Profile* profile,
@@ -56,6 +58,10 @@ class AppsModelBuilder : public content::NotificationObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // ui::ListModelObserver overrides:
   virtual void ListItemsAdded(size_t start, size_t count) OVERRIDE;
   virtual void ListItemsRemoved(size_t start, size_t count) OVERRIDE;
diff --git a/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc b/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
index 4d0fe51..cd8aef2 100644
--- a/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
+++ b/chrome/browser/ui/ash/launcher/chrome_launcher_controller.cc
@@ -784,25 +784,25 @@ void ChromeLauncherController::Observe(
       app_icon_loader_->ClearImage(extension->id());
       break;
     }
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      const std::string& pref_name(
-          *content::Details<std::string>(details).ptr());
-      if (pref_name == prefs::kPinnedLauncherApps) {
-        UpdateAppLaunchersFromPref();
-      } else if (pref_name == prefs::kShelfAlignmentLocal) {
-        SetShelfAlignmentFromPrefs();
-      } else if (pref_name == prefs::kShelfAutoHideBehaviorLocal) {
-        SetShelfAutoHideBehaviorFromPrefs();
-      } else {
-        NOTREACHED() << "Unexpected pref change for " << pref_name;
-      }
-      break;
-    }
     default:
       NOTREACHED() << "Unexpected notification type=" << type;
   }
 }
 
+void ChromeLauncherController::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  if (pref_name == prefs::kPinnedLauncherApps) {
+    UpdateAppLaunchersFromPref();
+  } else if (pref_name == prefs::kShelfAlignmentLocal) {
+    SetShelfAlignmentFromPrefs();
+  } else if (pref_name == prefs::kShelfAutoHideBehaviorLocal) {
+    SetShelfAutoHideBehaviorFromPrefs();
+  } else {
+    NOTREACHED() << "Unexpected pref change for " << pref_name;
+  }
+}
+
 void ChromeLauncherController::OnShelfAlignmentChanged() {
   const char* pref_value = NULL;
   // TODO(oshima): Support multiple displays.
diff --git a/chrome/browser/ui/ash/launcher/chrome_launcher_controller.h b/chrome/browser/ui/ash/launcher/chrome_launcher_controller.h
index e27982c..0c5a04b 100644
--- a/chrome/browser/ui/ash/launcher/chrome_launcher_controller.h
+++ b/chrome/browser/ui/ash/launcher/chrome_launcher_controller.h
@@ -18,6 +18,7 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/timer.h"
 #include "chrome/browser/api/sync/profile_sync_service_observer.h"
 #include "chrome/browser/prefs/pref_service_observer.h"
@@ -55,6 +56,7 @@ class ChromeLauncherController
       public ash::LauncherModelObserver,
       public ash::ShellObserver,
       public content::NotificationObserver,
+      public PrefObserver,
       public ProfileSyncServiceObserver,
       public PrefServiceObserver {
  public:
@@ -263,6 +265,10 @@ class ChromeLauncherController
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Overridden from ash::ShellObserver:
   virtual void OnShelfAlignmentChanged() OVERRIDE;
 
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index d8051d3..005d66c 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -1916,23 +1916,6 @@ void Browser::Observe(int type,
       break;
 #endif
 
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      const std::string& pref_name =
-          *content::Details<std::string>(details).ptr();
-      if (pref_name == prefs::kDevToolsDisabled) {
-        if (profile_->GetPrefs()->GetBoolean(prefs::kDevToolsDisabled))
-          content::DevToolsManager::GetInstance()->CloseAllClientHosts();
-      } else if (pref_name == prefs::kShowBookmarkBar) {
-        UpdateBookmarkBarState(BOOKMARK_BAR_STATE_CHANGE_PREF_CHANGE);
-      } else if (pref_name == prefs::kHomePage) {
-        PrefService* pref_service = content::Source<PrefService>(source).ptr();
-        MarkHomePageAsChanged(pref_service);
-      } else {
-        NOTREACHED();
-      }
-      break;
-    }
-
     case chrome::NOTIFICATION_WEB_CONTENT_SETTINGS_CHANGED: {
       WebContents* web_contents = content::Source<WebContents>(source).ptr();
       if (web_contents == chrome::GetActiveWebContents(this)) {
@@ -1956,6 +1939,20 @@ void Browser::Observe(int type,
   }
 }
 
+void Browser::OnPreferenceChanged(PrefServiceBase* service,
+                                  const std::string& pref_name) {
+  if (pref_name == prefs::kDevToolsDisabled) {
+    if (profile_->GetPrefs()->GetBoolean(prefs::kDevToolsDisabled))
+      content::DevToolsManager::GetInstance()->CloseAllClientHosts();
+  } else if (pref_name == prefs::kShowBookmarkBar) {
+    UpdateBookmarkBarState(BOOKMARK_BAR_STATE_CHANGE_PREF_CHANGE);
+  } else if (pref_name == prefs::kHomePage) {
+    MarkHomePageAsChanged(static_cast<PrefService*>(service));
+  } else {
+    NOTREACHED();
+  }
+}
+
 void Browser::ModeChanged(const chrome::search::Mode& old_mode,
                           const chrome::search::Mode& new_mode) {
   UpdateBookmarkBarState(BOOKMARK_BAR_STATE_CHANGE_TAB_STATE);
diff --git a/chrome/browser/ui/browser.h b/chrome/browser/ui/browser.h
index 76f82ee..a4148f2 100644
--- a/chrome/browser/ui/browser.h
+++ b/chrome/browser/ui/browser.h
@@ -16,6 +16,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string16.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/debugger/devtools_toggle_action.h"
@@ -36,6 +37,7 @@
 #include "chrome/common/content_settings.h"
 #include "chrome/common/content_settings_types.h"
 #include "chrome/common/extensions/extension_constants.h"
+#include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/page_navigator.h"
 #include "content/public/browser/web_contents_delegate.h"
@@ -106,6 +108,7 @@ class Browser : public TabStripModelObserver,
                 public ZoomObserver,
                 public content::PageNavigator,
                 public content::NotificationObserver,
+                public PrefObserver,
                 public ui::SelectFileDialog::Listener,
                 public chrome::search::SearchModelObserver {
  public:
@@ -691,6 +694,10 @@ class Browser : public TabStripModelObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Overridden from chrome::search::SearchModelObserver:
   virtual void ModeChanged(const chrome::search::Mode& old_mode,
                            const chrome::search::Mode& new_mode) OVERRIDE;
diff --git a/chrome/browser/ui/browser_command_controller.cc b/chrome/browser/ui/browser_command_controller.cc
index ae7c6db..b871deb 100644
--- a/chrome/browser/ui/browser_command_controller.cc
+++ b/chrome/browser/ui/browser_command_controller.cc
@@ -664,29 +664,6 @@ void BrowserCommandController::Observe(
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   switch (type) {
-    case NOTIFICATION_PREF_CHANGED: {
-      const std::string& pref_name =
-          *content::Details<std::string>(details).ptr();
-      if (pref_name == prefs::kPrintingEnabled) {
-        UpdatePrintingState();
-      } else if (pref_name == prefs::kIncognitoModeAvailability) {
-        UpdateCommandsForIncognitoAvailability();
-      } else if (pref_name == prefs::kDevToolsDisabled) {
-        UpdateCommandsForDevTools();
-      } else if (pref_name == prefs::kEditBookmarksEnabled) {
-        UpdateCommandsForBookmarkEditing();
-      } else if (pref_name == prefs::kShowBookmarkBar) {
-        UpdateCommandsForBookmarkBar();
-      } else if (pref_name == prefs::kAllowFileSelectionDialogs) {
-        UpdateSaveAsState();
-        UpdateOpenFileState();
-      } else if (pref_name == prefs::kInManagedMode) {
-        UpdateCommandsForMultipleProfiles();
-      } else {
-        NOTREACHED();
-      }
-      break;
-    }
     case content::NOTIFICATION_INTERSTITIAL_ATTACHED:
       UpdateCommandsForTabState();
       break;
@@ -701,6 +678,32 @@ void BrowserCommandController::Observe(
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+// PrefObserver implementation:
+
+void BrowserCommandController::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  if (pref_name == prefs::kPrintingEnabled) {
+    UpdatePrintingState();
+  } else if (pref_name == prefs::kIncognitoModeAvailability) {
+    UpdateCommandsForIncognitoAvailability();
+  } else if (pref_name == prefs::kDevToolsDisabled) {
+    UpdateCommandsForDevTools();
+  } else if (pref_name == prefs::kEditBookmarksEnabled) {
+    UpdateCommandsForBookmarkEditing();
+  } else if (pref_name == prefs::kShowBookmarkBar) {
+    UpdateCommandsForBookmarkBar();
+  } else if (pref_name == prefs::kAllowFileSelectionDialogs) {
+    UpdateSaveAsState();
+    UpdateOpenFileState();
+  } else if (pref_name == prefs::kInManagedMode) {
+    UpdateCommandsForMultipleProfiles();
+  } else {
+    NOTREACHED();
+  }
+}
+
+////////////////////////////////////////////////////////////////////////////////
 // BrowserCommandController, TabStripModelObserver implementation:
 
 void BrowserCommandController::TabInsertedAt(TabContents* contents,
diff --git a/chrome/browser/ui/browser_command_controller.h b/chrome/browser/ui/browser_command_controller.h
index ccce17c..5ef5b5c 100644
--- a/chrome/browser/ui/browser_command_controller.h
+++ b/chrome/browser/ui/browser_command_controller.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_UI_BROWSER_COMMAND_CONTROLLER_H_
 
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/sync/profile_sync_service_observer.h"
 #include "chrome/browser/command_updater.h"
 #include "chrome/browser/sessions/tab_restore_service_observer.h"
@@ -27,6 +28,7 @@ namespace chrome {
 
 class BrowserCommandController : public CommandUpdater::CommandUpdaterDelegate,
                                  public content::NotificationObserver,
+                                 public PrefObserver,
                                  public TabStripModelObserver,
                                  public TabRestoreServiceObserver,
                                  public ProfileSyncServiceObserver {
@@ -86,6 +88,10 @@ class BrowserCommandController : public CommandUpdater::CommandUpdaterDelegate,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Overridden from TabStripModelObserver:
   virtual void TabInsertedAt(TabContents* contents,
                              int index,
diff --git a/chrome/browser/ui/browser_instant_controller.cc b/chrome/browser/ui/browser_instant_controller.cc
index 66defb1..5f6319a 100644
--- a/chrome/browser/ui/browser_instant_controller.cc
+++ b/chrome/browser/ui/browser_instant_controller.cc
@@ -104,15 +104,12 @@ TabContents* BrowserInstantController::GetActiveTabContents() const {
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-// BrowserInstantController, content::NotificationObserver implementation:
-
-void BrowserInstantController::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(std::string(prefs::kInstantEnabled),
-            *content::Details<std::string>(details).ptr());
+// BrowserInstantController, PrefObserver implementation:
+
+void BrowserInstantController::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  DCHECK_EQ(std::string(prefs::kInstantEnabled), pref_name);
   ResetInstant();
 }
 
diff --git a/chrome/browser/ui/browser_instant_controller.h b/chrome/browser/ui/browser_instant_controller.h
index 24e6868..13a1e2f 100644
--- a/chrome/browser/ui/browser_instant_controller.h
+++ b/chrome/browser/ui/browser_instant_controller.h
@@ -9,12 +9,12 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string16.h"
 #include "chrome/browser/instant/instant_unload_handler.h"
 #include "chrome/browser/ui/search/search_model_observer.h"
 #include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
 #include "chrome/common/instant_types.h"
-#include "content/public/browser/notification_observer.h"
 #include "webkit/glue/window_open_disposition.h"
 
 class Browser;
@@ -22,11 +22,6 @@ class InstantController;
 class InstantTest;
 class TabContents;
 
-namespace content {
-class NotificationDetails;
-class NotificationSource;
-}
-
 namespace gfx {
 class Rect;
 }
@@ -35,7 +30,7 @@ namespace chrome {
 
 class BrowserInstantController : public TabStripModelObserver,
                                  public search::SearchModelObserver,
-                                 public content::NotificationObserver {
+                                 public PrefObserver {
  public:
   explicit BrowserInstantController(Browser* browser);
   virtual ~BrowserInstantController();
@@ -67,10 +62,9 @@ class BrowserInstantController : public TabStripModelObserver,
   // preview would be shown.
   TabContents* GetActiveTabContents() const;
 
-  // Overridden from content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Overridden from TabStripModelObserver:
   virtual void TabDeactivated(TabContents* contents) OVERRIDE;
diff --git a/chrome/browser/ui/cocoa/browser_window_cocoa.h b/chrome/browser/ui/cocoa/browser_window_cocoa.h
index d815aba..fd9c923e 100644
--- a/chrome/browser/ui/cocoa/browser_window_cocoa.h
+++ b/chrome/browser/ui/cocoa/browser_window_cocoa.h
@@ -8,10 +8,10 @@
 #include "base/memory/scoped_nsobject.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/bookmarks/bookmark_model.h"
 #include "chrome/browser/extensions/extension_keybinding_registry.h"
 #include "chrome/browser/ui/browser_window.h"
-#include "content/public/browser/notification_registrar.h"
 #include "ui/base/ui_base_types.h"
 
 class Browser;
@@ -32,7 +32,7 @@ class Extension;
 
 class BrowserWindowCocoa :
     public BrowserWindow,
-    public content::NotificationObserver,
+    public PrefObserver,
     public extensions::ExtensionKeybindingRegistry::Delegate {
  public:
   BrowserWindowCocoa(Browser* browser,
@@ -147,9 +147,8 @@ class BrowserWindowCocoa :
   virtual void ShowAvatarBubbleFromAvatarButton() OVERRIDE;
 
   // Overridden from NotificationObserver
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Overridden from ExtensionKeybindingRegistry::Delegate:
   virtual extensions::ActiveTabPermissionGranter*
@@ -167,7 +166,6 @@ class BrowserWindowCocoa :
  private:
   NSWindow* window() const;  // Accessor for the (current) |NSWindow|.
 
-  content::NotificationRegistrar registrar_;
   PrefChangeRegistrar pref_change_registrar_;
   Browser* browser_;  // weak, owned by controller
   BrowserWindowController* controller_;  // weak, owns us
diff --git a/chrome/browser/ui/cocoa/browser_window_cocoa.mm b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
index b15fb7c..1c875c6 100644
--- a/chrome/browser/ui/cocoa/browser_window_cocoa.mm
+++ b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
@@ -614,21 +614,10 @@ bool BrowserWindowCocoa::GetConstrainedWindowTopY(int* top_y) {
   return false;
 }
 
-void BrowserWindowCocoa::Observe(int type,
-                                 const content::NotificationSource& source,
-                                 const content::NotificationDetails& details) {
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      const std::string& pref_name =
-          *content::Details<std::string>(details).ptr();
-      DCHECK(pref_name == prefs::kShowBookmarkBar);
-      [controller_ updateBookmarkBarVisibilityWithAnimation:YES];
-      break;
-    }
-    default:
-      NOTREACHED();  // we don't ask for anything else!
-      break;
-  }
+void BrowserWindowCocoa::OnPreferenceChanged(PrefServiceBase* service,
+                                             const std::string& pref_name) {
+  DCHECK(pref_name == prefs::kShowBookmarkBar);
+  [controller_ updateBookmarkBarVisibilityWithAnimation:YES];
 }
 
 extensions::ActiveTabPermissionGranter*
diff --git a/chrome/browser/ui/cocoa/browser_window_cocoa_unittest.mm b/chrome/browser/ui/cocoa/browser_window_cocoa_unittest.mm
index e5814f8..1e2f4ce 100644
--- a/chrome/browser/ui/cocoa/browser_window_cocoa_unittest.mm
+++ b/chrome/browser/ui/cocoa/browser_window_cocoa_unittest.mm
@@ -4,6 +4,7 @@
 
 #include "base/memory/scoped_nsobject.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string_util.h"
 #include "chrome/browser/bookmarks/bookmark_utils.h"
 #import "chrome/browser/ui/cocoa/browser_window_cocoa.h"
@@ -19,7 +20,7 @@
 // A BrowserWindowCocoa that goes PONG when
 // BOOKMARK_BAR_VISIBILITY_PREF_CHANGED is sent.  This is so we can be
 // sure we are observing it.
-class BrowserWindowCocoaPong : public BrowserWindowCocoa {
+class BrowserWindowCocoaPong : public BrowserWindowCocoa, public PrefObserver {
  public:
   BrowserWindowCocoaPong(Browser* browser,
                          BrowserWindowController* controller)
@@ -28,16 +29,10 @@ class BrowserWindowCocoaPong : public BrowserWindowCocoa {
   }
   virtual ~BrowserWindowCocoaPong() { }
 
-  void Observe(int type,
-               const content::NotificationSource& source,
-               const content::NotificationDetails& details) {
-    if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-      const std::string& pref_name =
-          *content::Details<std::string>(details).ptr();
-      if (pref_name == prefs::kShowBookmarkBar)
-        pong_ = true;
-    }
-    BrowserWindowCocoa::Observe(type, source, details);
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE {
+    if (pref_name == prefs::kShowBookmarkBar)
+      pong_ = true;
   }
 
   bool pong_;
diff --git a/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h b/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h
index 3290143..bba88ff 100644
--- a/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h
+++ b/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h
@@ -13,6 +13,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/extensions/image_loading_tracker.h"
 #include "chrome/browser/ui/browser.h"
@@ -45,7 +46,8 @@ class ZoomDecoration;
 class LocationBarViewMac : public LocationBar,
                            public LocationBarTesting,
                            public OmniboxEditController,
-                           public content::NotificationObserver {
+                           public content::NotificationObserver,
+                           public PrefObserver {
  public:
   LocationBarViewMac(AutocompleteTextField* field,
                      CommandUpdater* command_updater,
@@ -181,6 +183,10 @@ class LocationBarViewMac : public LocationBar,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   Browser* browser() const { return browser_; }
 
  private:
diff --git a/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm b/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
index b560bcd..1148992 100644
--- a/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
+++ b/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
@@ -593,17 +593,18 @@ void LocationBarViewMac::Observe(int type,
       break;
     }
 
-    case chrome::NOTIFICATION_PREF_CHANGED:
-      UpdateStarDecorationVisibility();
-      OnChanged();
-      break;
-
     default:
       NOTREACHED() << "Unexpected notification";
       break;
   }
 }
 
+void LocationBarViewMac::OnPreferenceChanged(PrefServiceBase* service,
+                                             const std::string& pref_name) {
+  UpdateStarDecorationVisibility();
+  OnChanged();
+}
+
 void LocationBarViewMac::PostNotification(NSString* notification) {
   [[NSNotificationCenter defaultCenter] postNotificationName:notification
                                         object:[NSValue valueWithPointer:this]];
diff --git a/chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm b/chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm
index 91f2fee..39f326e 100644
--- a/chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm
+++ b/chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm
@@ -9,6 +9,7 @@
 #include "base/mac/bundle_locations.h"
 #include "base/mac/mac_util.h"
 #include "base/memory/singleton.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string_util.h"
 #include "base/sys_string_conversions.h"
 #include "base/utf_string_conversions.h"
@@ -87,7 +88,7 @@ const CGFloat kWrenchMenuLeftPadding = 3.0;
 @property(assign, nonatomic) Browser* browser;
 - (void)addAccessibilityDescriptions;
 - (void)initCommandStatus:(CommandUpdater*)commands;
-- (void)prefChanged:(std::string*)prefName;
+- (void)prefChanged:(const std::string&)prefName;
 - (BackgroundGradientView*)backgroundGradientView;
 - (void)toolbarFrameChanged;
 - (void)pinLocationBarToLeftOfBrowserActionsContainerAndAnimate:(BOOL)animate;
@@ -105,7 +106,9 @@ namespace ToolbarControllerInternal {
 // A class registered for C++ notifications. This is used to detect changes in
 // preferences and upgrade available notifications. Bridges the notification
 // back to the ToolbarController.
-class NotificationBridge : public content::NotificationObserver {
+class NotificationBridge
+    : public content::NotificationObserver,
+      public PrefObserver {
  public:
   explicit NotificationBridge(ToolbarController* controller)
       : controller_(controller) {
@@ -118,11 +121,8 @@ class NotificationBridge : public content::NotificationObserver {
   // Overridden from content::NotificationObserver:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
-                       const content::NotificationDetails& details) {
+                       const content::NotificationDetails& details) OVERRIDE {
     switch (type) {
-      case chrome::NOTIFICATION_PREF_CHANGED:
-        [controller_ prefChanged:content::Details<std::string>(details).ptr()];
-        break;
       case chrome::NOTIFICATION_UPGRADE_RECOMMENDED:
       case chrome::NOTIFICATION_GLOBAL_ERRORS_CHANGED:
         [controller_ badgeWrenchMenuIfNeeded];
@@ -132,6 +132,12 @@ class NotificationBridge : public content::NotificationObserver {
     }
   }
 
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE {
+    [controller_ prefChanged:pref_name];
+  }
+
  private:
   ToolbarController* controller_;  // weak, owns us
 
@@ -563,9 +569,8 @@ class NotificationBridge : public content::NotificationObserver {
   [[wrenchButton_ cell] setOverlayImageID:error_badge_id];
 }
 
-- (void)prefChanged:(std::string*)prefName {
-  if (!prefName) return;
-  if (*prefName == prefs::kShowHomeButton) {
+- (void)prefChanged:(const std::string&)prefName {
+  if (prefName == prefs::kShowHomeButton) {
     [self showOptionalHomeButton];
   }
 }
diff --git a/chrome/browser/ui/gesture_prefs_observer_factory_aura.cc b/chrome/browser/ui/gesture_prefs_observer_factory_aura.cc
index 16fa3ef..5cd51d3 100644
--- a/chrome/browser/ui/gesture_prefs_observer_factory_aura.cc
+++ b/chrome/browser/ui/gesture_prefs_observer_factory_aura.cc
@@ -6,6 +6,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_dependency_manager.h"
@@ -19,7 +20,7 @@ using ui::GestureConfiguration;
 namespace {
 
 // This class manages gesture configuration preferences.
-class GesturePrefsObserver : public content::NotificationObserver,
+class GesturePrefsObserver : public PrefObserver,
                              public ProfileKeyedService {
  public:
   explicit GesturePrefsObserver(PrefService* prefs);
@@ -28,10 +29,9 @@ class GesturePrefsObserver : public content::NotificationObserver,
   // ProfileKeyedService implementation.
   virtual void Shutdown() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   void Update();
@@ -81,10 +81,8 @@ void GesturePrefsObserver::Shutdown() {
   registrar_.RemoveAll();
 }
 
-void GesturePrefsObserver::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void GesturePrefsObserver::OnPreferenceChanged(PrefServiceBase* service,
+                                               const std::string& pref_name) {
   Update();
 }
 
diff --git a/chrome/browser/ui/gtk/bookmarks/bookmark_bar_gtk.cc b/chrome/browser/ui/gtk/bookmarks/bookmark_bar_gtk.cc
index 3b1b912..7f1b30b 100644
--- a/chrome/browser/ui/gtk/bookmarks/bookmark_bar_gtk.cc
+++ b/chrome/browser/ui/gtk/bookmarks/bookmark_bar_gtk.cc
@@ -980,14 +980,15 @@ void BookmarkBarGtk::Observe(int type,
     }
 
     SetOverflowButtonAppearance();
-  } else if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    const std::string& pref_name =
-        *content::Details<std::string>(details).ptr();
-    if (pref_name == prefs::kEditBookmarksEnabled)
-      OnEditBookmarksEnabledChanged();
   }
 }
 
+void BookmarkBarGtk::OnPreferenceChanged(PrefServiceBase* service,
+                                         const std::string& pref_name) {
+  if (pref_name == prefs::kEditBookmarksEnabled)
+    OnEditBookmarksEnabledChanged();
+}
+
 GtkWidget* BookmarkBarGtk::CreateBookmarkButton(const BookmarkNode* node) {
   GtkWidget* button = theme_service_->BuildChromeButton();
   bookmark_utils::ConfigureButtonForNode(node, model_, button, theme_service_);
diff --git a/chrome/browser/ui/gtk/bookmarks/bookmark_bar_gtk.h b/chrome/browser/ui/gtk/bookmarks/bookmark_bar_gtk.h
index 774c076..61f78a6 100644
--- a/chrome/browser/ui/gtk/bookmarks/bookmark_bar_gtk.h
+++ b/chrome/browser/ui/gtk/bookmarks/bookmark_bar_gtk.h
@@ -13,6 +13,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/bookmarks/bookmark_model_observer.h"
 #include "chrome/browser/ui/bookmarks/bookmark_bar.h"
@@ -46,6 +47,7 @@ class BookmarkBarGtk : public ui::AnimationDelegate,
                        public BookmarkModelObserver,
                        public MenuBarHelper::Delegate,
                        public content::NotificationObserver,
+                       public PrefObserver,
                        public chrome::BookmarkBarInstructionsDelegate,
                        public BookmarkContextMenuControllerDelegate {
  public:
@@ -236,6 +238,11 @@ class BookmarkBarGtk : public ui::AnimationDelegate,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
+
   GtkWidget* CreateBookmarkButton(const BookmarkNode* node);
   GtkToolItem* CreateBookmarkToolItem(const BookmarkNode* node);
 
diff --git a/chrome/browser/ui/gtk/browser_toolbar_gtk.cc b/chrome/browser/ui/gtk/browser_toolbar_gtk.cc
index d272e1e..6919a515 100644
--- a/chrome/browser/ui/gtk/browser_toolbar_gtk.cc
+++ b/chrome/browser/ui/gtk/browser_toolbar_gtk.cc
@@ -250,6 +250,7 @@ void BrowserToolbarGtk::Init(GtkWindow* top_level_window) {
     if (actions_toolbar_->button_count() == 0)
       gtk_widget_hide(actions_toolbar_->widget());
   }
+
   // Initialize pref-dependent UI state.
   NotifyPrefChanged(NULL);
 
@@ -368,9 +369,7 @@ bool BrowserToolbarGtk::GetAcceleratorForCommandId(
 void BrowserToolbarGtk::Observe(int type,
                                 const content::NotificationSource& source,
                                 const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    NotifyPrefChanged(content::Details<std::string>(details).ptr());
-  } else if (type == chrome::NOTIFICATION_BROWSER_THEME_CHANGED) {
+  if (type == chrome::NOTIFICATION_BROWSER_THEME_CHANGED) {
     // Update the spacing around the menu buttons
     bool use_gtk = theme_service_->UsingNativeTheme();
     int border = use_gtk ? 0 : 2;
@@ -426,6 +425,11 @@ void BrowserToolbarGtk::Observe(int type,
   }
 }
 
+void BrowserToolbarGtk::OnPreferenceChanged(PrefServiceBase* service,
+                                            const std::string& pref_name) {
+  NotifyPrefChanged(&pref_name);
+}
+
 // BrowserToolbarGtk, public ---------------------------------------------------
 
 void BrowserToolbarGtk::UpdateWebContents(WebContents* contents,
diff --git a/chrome/browser/ui/gtk/browser_toolbar_gtk.h b/chrome/browser/ui/gtk/browser_toolbar_gtk.h
index e8e6617..1d141e4 100644
--- a/chrome/browser/ui/gtk/browser_toolbar_gtk.h
+++ b/chrome/browser/ui/gtk/browser_toolbar_gtk.h
@@ -10,6 +10,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/command_observer.h"
 #include "chrome/browser/ui/gtk/custom_button.h"
@@ -43,7 +44,8 @@ class WebContents;
 class BrowserToolbarGtk : public CommandObserver,
                           public ui::AcceleratorProvider,
                           public MenuGtk::Delegate,
-                          public content::NotificationObserver {
+                          public content::NotificationObserver,
+                          public PrefObserver {
  public:
   BrowserToolbarGtk(Browser* browser, BrowserWindowGtk* window);
   virtual ~BrowserToolbarGtk();
@@ -104,6 +106,10 @@ class BrowserToolbarGtk : public CommandObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Whether the wrench/hotdogs menu is currently visible to the user.
   bool IsWrenchMenuShowing() const;
 
@@ -143,7 +149,7 @@ class BrowserToolbarGtk : public CommandObserver,
   CHROMEGTK_CALLBACK_1(BrowserToolbarGtk, gboolean, OnWrenchMenuButtonExpose,
                        GdkEventExpose*);
 
-  // Updates preference-dependent state.
+  // Updates preference-dependent state. |pref| may be NULL.
   void NotifyPrefChanged(const std::string* pref);
 
   static void SetSyncMenuLabel(GtkWidget* widget, gpointer userdata);
diff --git a/chrome/browser/ui/gtk/browser_window_gtk.cc b/chrome/browser/ui/gtk/browser_window_gtk.cc
index 92a4ba3..755521d 100644
--- a/chrome/browser/ui/gtk/browser_window_gtk.cc
+++ b/chrome/browser/ui/gtk/browser_window_gtk.cc
@@ -1185,26 +1185,22 @@ void BrowserWindowGtk::ConfirmBrowserCloseWithPendingDownloads() {
 void BrowserWindowGtk::Observe(int type,
                                const content::NotificationSource& source,
                                const content::NotificationDetails& details) {
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      std::string* pref_name = content::Details<std::string>(details).ptr();
-      if (*pref_name == prefs::kUseCustomChromeFrame) {
-        UpdateCustomFrame();
-        ui::SetHideTitlebarWhenMaximizedProperty(
-            ui::GetX11WindowFromGtkWidget(GTK_WIDGET(window_)),
-            UseCustomFrame() ? ui::HIDE_TITLEBAR_WHEN_MAXIMIZED
-                             : ui::SHOW_TITLEBAR_WHEN_MAXIMIZED);
-      } else {
-        NOTREACHED() << "Got pref change notification we didn't register for!";
-      }
-      break;
-    }
-    case chrome::NOTIFICATION_PROFILE_CACHED_INFO_CHANGED:
-      // The profile avatar icon may have changed.
-      gtk_util::SetWindowIcon(window_, browser_->profile());
-      break;
-    default:
-      break;
+  DCHECK_EQ(chrome::NOTIFICATION_PROFILE_CACHED_INFO_CHANGED, type);
+  // The profile avatar icon may have changed.
+  gtk_util::SetWindowIcon(window_, browser_->profile());
+}
+
+void BrowserWindowGtk::OnPreferenceChanged(PrefServiceBase* service,
+                                           const std::string& pref_name) {
+  if (pref_name == prefs::kUseCustomChromeFrame) {
+    UpdateCustomFrame();
+    ui::SetHideTitlebarWhenMaximizedProperty(
+        ui::GetX11WindowFromGtkWidget(GTK_WIDGET(window_)),
+        UseCustomFrame() ?
+            ui::HIDE_TITLEBAR_WHEN_MAXIMIZED :
+            ui::SHOW_TITLEBAR_WHEN_MAXIMIZED);
+  } else {
+    NOTREACHED() << "Got pref change notification we didn't register for!";
   }
 }
 
diff --git a/chrome/browser/ui/gtk/browser_window_gtk.h b/chrome/browser/ui/gtk/browser_window_gtk.h
index c0015c2..7c2e5d0 100644
--- a/chrome/browser/ui/gtk/browser_window_gtk.h
+++ b/chrome/browser/ui/gtk/browser_window_gtk.h
@@ -12,6 +12,7 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/timer.h"
 #include "build/build_config.h"
 #include "chrome/browser/api/prefs/pref_member.h"
@@ -60,6 +61,7 @@ class Extension;
 class BrowserWindowGtk
     : public BrowserWindow,
       public content::NotificationObserver,
+      public PrefObserver,
       public TabStripModelObserver,
       public ui::ActiveWindowWatcherXObserver,
       public InfoBarContainer::Delegate,
@@ -181,6 +183,10 @@ class BrowserWindowGtk
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Overridden from TabStripModelObserver:
   virtual void TabDetachedAt(TabContents* contents, int index) OVERRIDE;
   virtual void ActiveTabChanged(TabContents* old_contents,
diff --git a/chrome/browser/ui/gtk/global_menu_bar.cc b/chrome/browser/ui/gtk/global_menu_bar.cc
index 7ea211d..31cf7fc 100644
--- a/chrome/browser/ui/gtk/global_menu_bar.cc
+++ b/chrome/browser/ui/gtk/global_menu_bar.cc
@@ -281,11 +281,8 @@ void GlobalMenuBar::EnabledStateChangedForCommand(int id, bool enabled) {
     gtk_widget_set_sensitive(it->second, enabled);
 }
 
-void GlobalMenuBar::Observe(int type,
-                            const content::NotificationSource& source,
-                            const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  const std::string& pref_name = *content::Details<std::string>(details).ptr();
+void GlobalMenuBar::OnPreferenceChanged(PrefServiceBase* service,
+                                        const std::string& pref_name) {
   DCHECK_EQ(prefs::kShowBookmarkBar, pref_name);
   OnBookmarkBarVisibilityChanged();
 }
diff --git a/chrome/browser/ui/gtk/global_menu_bar.h b/chrome/browser/ui/gtk/global_menu_bar.h
index ba72f89..a1682d6 100644
--- a/chrome/browser/ui/gtk/global_menu_bar.h
+++ b/chrome/browser/ui/gtk/global_menu_bar.h
@@ -9,9 +9,9 @@
 
 #include "base/compiler_specific.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/command_observer.h"
 #include "chrome/browser/ui/gtk/global_history_menu.h"
-#include "content/public/browser/notification_observer.h"
 #include "ui/base/gtk/gtk_signal.h"
 #include "ui/base/gtk/owned_widget_gtk.h"
 
@@ -31,7 +31,7 @@ typedef struct _GtkWidget GtkWidget;
 // bar itself is visible, so we insert a GtkMenuBar into the window hierarchy
 // and set it to be invisible.
 class GlobalMenuBar : public CommandObserver,
-                      public content::NotificationObserver {
+                      public PrefObserver {
  public:
   static const int TAG_NORMAL = 0;
   static const int TAG_MOST_VISITED = 1;
@@ -68,10 +68,9 @@ class GlobalMenuBar : public CommandObserver,
   // CommandObserver:
   virtual void EnabledStateChangedForCommand(int id, bool enabled) OVERRIDE;
 
-  // content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Updates the visibility of the bookmark bar on pref changes.
   void OnBookmarkBarVisibilityChanged();
diff --git a/chrome/browser/ui/gtk/gtk_theme_service.cc b/chrome/browser/ui/gtk/gtk_theme_service.cc
index 814c535..cfb3368 100644
--- a/chrome/browser/ui/gtk/gtk_theme_service.cc
+++ b/chrome/browser/ui/gtk/gtk_theme_service.cc
@@ -367,15 +367,10 @@ bool GtkThemeService::UsingNativeTheme() const {
   return use_gtk_;
 }
 
-void GtkThemeService::Observe(int type,
-                              const content::NotificationSource& source,
-                              const content::NotificationDetails& details) {
-  if ((type == chrome::NOTIFICATION_PREF_CHANGED) &&
-      (*content::Details<std::string>(details).ptr() ==
-          prefs::kUsesSystemTheme)) {
+void GtkThemeService::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
+  if (pref_name == prefs::kUsesSystemTheme) {
     use_gtk_ = profile()->GetPrefs()->GetBoolean(prefs::kUsesSystemTheme);
-  } else {
-    ThemeService::Observe(type, source, details);
   }
 }
 
diff --git a/chrome/browser/ui/gtk/gtk_theme_service.h b/chrome/browser/ui/gtk/gtk_theme_service.h
index 12dba20..1d4f147 100644
--- a/chrome/browser/ui/gtk/gtk_theme_service.h
+++ b/chrome/browser/ui/gtk/gtk_theme_service.h
@@ -12,8 +12,8 @@
 #include "base/lazy_instance.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/themes/theme_service.h"
-#include "content/public/browser/notification_observer.h"
 #include "ui/base/glib/glib_integers.h"
 #include "ui/base/gtk/gtk_signal.h"
 #include "ui/base/gtk/owned_widget_gtk.h"
@@ -41,7 +41,7 @@ typedef struct _GtkStyle GtkStyle;
 typedef struct _GtkWidget GtkWidget;
 
 // Specialization of ThemeService which supplies system colors.
-class GtkThemeService : public ThemeService {
+class GtkThemeService : public ThemeService, public PrefObserver {
  public:
   // A list of integer keys for a separate PerDisplaySurfaceMap that keeps
   // what would otherwise be static icons on the X11 server.
@@ -77,10 +77,9 @@ class GtkThemeService : public ThemeService {
   virtual bool UsingDefaultTheme() const OVERRIDE;
   virtual bool UsingNativeTheme() const OVERRIDE;
 
-  // Overridden from ThemeService, content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Creates a GtkChromeButton instance, registered with this theme provider,
   // with a "destroy" signal to remove it from our internal list when it goes
diff --git a/chrome/browser/ui/gtk/location_bar_view_gtk.cc b/chrome/browser/ui/gtk/location_bar_view_gtk.cc
index a90d22f..083b28d 100644
--- a/chrome/browser/ui/gtk/location_bar_view_gtk.cc
+++ b/chrome/browser/ui/gtk/location_bar_view_gtk.cc
@@ -1103,17 +1103,6 @@ void LocationBarViewGtk::Observe(int type,
       break;
     }
 
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      std::string* pref_name_in = content::Details<std::string>(details).ptr();
-      DCHECK(pref_name_in);
-
-      if (*pref_name_in == prefs::kEditBookmarksEnabled)
-        UpdateStarIcon();
-      else
-        NOTREACHED();
-      break;
-    }
-
     case chrome::NOTIFICATION_BROWSER_THEME_CHANGED: {
       if (theme_service_->UsingNativeTheme()) {
         gtk_widget_modify_bg(tab_to_search_box_, GTK_STATE_NORMAL, NULL);
@@ -1176,6 +1165,14 @@ void LocationBarViewGtk::Observe(int type,
   }
 }
 
+void LocationBarViewGtk::OnPreferenceChanged(PrefServiceBase* service,
+                                             const std::string& pref_name) {
+  if (pref_name == prefs::kEditBookmarksEnabled)
+    UpdateStarIcon();
+  else
+    NOTREACHED();
+}
+
 gboolean LocationBarViewGtk::HandleExpose(GtkWidget* widget,
                                           GdkEventExpose* event) {
   // If we're not using GTK theming, draw our own border over the edge pixels
diff --git a/chrome/browser/ui/gtk/location_bar_view_gtk.h b/chrome/browser/ui/gtk/location_bar_view_gtk.h
index f243c40..fee357d 100644
--- a/chrome/browser/ui/gtk/location_bar_view_gtk.h
+++ b/chrome/browser/ui/gtk/location_bar_view_gtk.h
@@ -16,6 +16,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/extensions/extension_action.h"
 #include "chrome/browser/extensions/extension_action_icon_factory.h"
@@ -61,7 +62,8 @@ class AcceleratorGtk;
 class LocationBarViewGtk : public OmniboxEditController,
                            public LocationBar,
                            public LocationBarTesting,
-                           public content::NotificationObserver {
+                           public content::NotificationObserver,
+                           public PrefObserver {
  public:
   explicit LocationBarViewGtk(Browser* browser);
   virtual ~LocationBarViewGtk();
@@ -165,6 +167,10 @@ class LocationBarViewGtk : public OmniboxEditController,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Edit background color.
   static const GdkColor kBackgroundColor;
 
diff --git a/chrome/browser/ui/prefs/prefs_tab_helper.cc b/chrome/browser/ui/prefs/prefs_tab_helper.cc
index 8074e6d..1d3e3d4 100644
--- a/chrome/browser/ui/prefs/prefs_tab_helper.cc
+++ b/chrome/browser/ui/prefs/prefs_tab_helper.cc
@@ -137,7 +137,7 @@ void RegisterFontFamilyMap(PrefService* prefs, const char* map_name) {
 // Registers |obs| to observe per-script font prefs under the path |map_name|.
 void RegisterFontFamilyMapObserver(PrefChangeRegistrar* registrar,
                                    const char* map_name,
-                                   content::NotificationObserver* obs) {
+                                   PrefObserver* obs) {
   for (size_t i = 0; i < prefs::kWebKitScriptsForFontFamilyMapsLength; ++i) {
     const char* script = prefs::kWebKitScriptsForFontFamilyMaps[i];
     std::string pref_name = base::StringPrintf("%s.%s", map_name, script);
@@ -566,27 +566,26 @@ void PrefsTabHelper::Observe(int type,
       break;
     }
 #endif
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      std::string* pref_name_in = content::Details<std::string>(details).ptr();
-      DCHECK(content::Source<PrefService>(source).ptr() ==
-                 GetProfile()->GetPrefs());
-      if (*pref_name_in == prefs::kDefaultCharset ||
-          StartsWithASCII(*pref_name_in, "webkit.webprefs.", true)) {
-        OnWebPrefChanged(*pref_name_in);
-      } else if (*pref_name_in == prefs::kDefaultZoomLevel ||
-                 *pref_name_in == prefs::kEnableReferrers ||
-                 *pref_name_in == prefs::kEnableDoNotTrack) {
-        UpdateRendererPreferences();
-      } else {
-        NOTREACHED() << "unexpected pref change notification" << *pref_name_in;
-      }
-      break;
-    }
     default:
       NOTREACHED();
   }
 }
 
+void PrefsTabHelper::OnPreferenceChanged(PrefServiceBase* service,
+                                         const std::string& pref_name_in) {
+  DCHECK_EQ(GetProfile()->GetPrefs(), service);
+  if (pref_name_in == prefs::kDefaultCharset ||
+      StartsWithASCII(pref_name_in, "webkit.webprefs.", true)) {
+    OnWebPrefChanged(pref_name_in);
+  } else if (pref_name_in == prefs::kDefaultZoomLevel ||
+             pref_name_in == prefs::kEnableReferrers ||
+             pref_name_in == prefs::kEnableDoNotTrack) {
+    UpdateRendererPreferences();
+  } else {
+    NOTREACHED() << "unexpected pref change notification" << pref_name_in;
+  }
+}
+
 void PrefsTabHelper::UpdateWebPreferences() {
   web_contents_->GetRenderViewHost()->UpdateWebkitPreferences(
       web_contents_->GetRenderViewHost()->GetWebkitPreferences());
diff --git a/chrome/browser/ui/prefs/prefs_tab_helper.h b/chrome/browser/ui/prefs/prefs_tab_helper.h
index cfb808b..5dc8c98 100644
--- a/chrome/browser/ui/prefs/prefs_tab_helper.h
+++ b/chrome/browser/ui/prefs/prefs_tab_helper.h
@@ -7,6 +7,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_contents_user_data.h"
@@ -21,6 +22,7 @@ class WebContents;
 
 // Per-tab class to handle user preferences.
 class PrefsTabHelper : public content::NotificationObserver,
+                       public PrefObserver,
                        public content::WebContentsUserData<PrefsTabHelper> {
  public:
   virtual ~PrefsTabHelper();
@@ -41,6 +43,10 @@ class PrefsTabHelper : public content::NotificationObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver overrides:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Update the WebContents's RendererPreferences.
   void UpdateRendererPreferences();
 
diff --git a/chrome/browser/ui/views/location_bar/location_bar_view.cc b/chrome/browser/ui/views/location_bar/location_bar_view.cc
index 9812e5d..0ffc957 100644
--- a/chrome/browser/ui/views/location_bar/location_bar_view.cc
+++ b/chrome/browser/ui/views/location_bar/location_bar_view.cc
@@ -1574,13 +1574,6 @@ void LocationBarView::Observe(int type,
                               const content::NotificationSource& source,
                               const content::NotificationDetails& details) {
   switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      std::string* name = content::Details<std::string>(details).ptr();
-      if (*name == prefs::kEditBookmarksEnabled)
-        Update(NULL);
-      break;
-    }
-
     case chrome::NOTIFICATION_EXTENSION_LOCATION_BAR_UPDATED: {
       // Only update if the updated action box was for the active tab contents.
       WebContents* target_tab = content::Details<WebContents>(details).ptr();
@@ -1594,6 +1587,12 @@ void LocationBarView::Observe(int type,
   }
 }
 
+void LocationBarView::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
+  if (pref_name == prefs::kEditBookmarksEnabled)
+    Update(NULL);
+}
+
 int LocationBarView::GetInternalHeight(bool use_preferred_size) {
   int total_height =
       use_preferred_size ? GetPreferredSize().height() : height();
diff --git a/chrome/browser/ui/views/location_bar/location_bar_view.h b/chrome/browser/ui/views/location_bar/location_bar_view.h
index e96819d..73b8437 100644
--- a/chrome/browser/ui/views/location_bar/location_bar_view.h
+++ b/chrome/browser/ui/views/location_bar/location_bar_view.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/extensions/extension_context_menu_model.h"
 #include "chrome/browser/search_engines/template_url_service_observer.h"
@@ -79,7 +80,8 @@ class LocationBarView : public LocationBar,
                         public DropdownBarHostDelegate,
                         public chrome::search::SearchModelObserver,
                         public TemplateURLServiceObserver,
-                        public content::NotificationObserver {
+                        public content::NotificationObserver,
+                        public PrefObserver {
  public:
   // The location bar view's class name.
   static const char kViewClassName[];
@@ -338,6 +340,10 @@ class LocationBarView : public LocationBar,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Overridden from PrefObserver
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Returns the height of the control without the top and bottom
   // edges(i.e.  the height of the edit control inside).  If
   // |use_preferred_size| is true this will be the preferred height,
diff --git a/chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc b/chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc
index 3f62535..21c31e9 100644
--- a/chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc
+++ b/chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc
@@ -442,20 +442,11 @@ void BrowserTabStripController::TabBlockedStateChanged(TabContents* contents,
 ////////////////////////////////////////////////////////////////////////////////
 // BrowserTabStripController, content::NotificationObserver implementation:
 
-void BrowserTabStripController::Observe(int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED:
-      if (*content::Details<std::string>(details).ptr() ==
-          prefs::kTabStripLayoutType) {
-        UpdateLayoutType();
-      }
-      break;
-
-    default:
-      NOTREACHED();
-      break;
+void BrowserTabStripController::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  if (pref_name == prefs::kTabStripLayoutType) {
+    UpdateLayoutType();
   }
 }
 
diff --git a/chrome/browser/ui/views/tabs/browser_tab_strip_controller.h b/chrome/browser/ui/views/tabs/browser_tab_strip_controller.h
index 1a5e852..64dbd2d 100644
--- a/chrome/browser/ui/views/tabs/browser_tab_strip_controller.h
+++ b/chrome/browser/ui/views/tabs/browser_tab_strip_controller.h
@@ -8,10 +8,10 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/ui/tabs/hover_tab_selector.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/views/tabs/tab_strip_controller.h"
-#include "content/public/browser/notification_observer.h"
 
 class BaseTab;
 class Browser;
@@ -28,7 +28,7 @@ class WebContents;
 // TabContentses in a TabStripModel.
 class BrowserTabStripController : public TabStripController,
                                   public TabStripModelObserver,
-                                  public content::NotificationObserver {
+                                  public PrefObserver {
  public:
   BrowserTabStripController(Browser* browser, TabStripModel* model);
   virtual ~BrowserTabStripController();
@@ -97,10 +97,9 @@ class BrowserTabStripController : public TabStripController,
   virtual void TabBlockedStateChanged(TabContents* contents,
                                       int model_index) OVERRIDE;
 
-  // content::NotificationObserver implementation:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  protected:
   // The context in which SetTabRendererDataFromModel is being called.
diff --git a/chrome/browser/ui/views/toolbar_view.cc b/chrome/browser/ui/views/toolbar_view.cc
index 31076d1..7f91d3f 100644
--- a/chrome/browser/ui/views/toolbar_view.cc
+++ b/chrome/browser/ui/views/toolbar_view.cc
@@ -528,14 +528,6 @@ void ToolbarView::Observe(int type,
                           const content::NotificationSource& source,
                           const content::NotificationDetails& details) {
   switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      std::string* pref_name = content::Details<std::string>(details).ptr();
-      if (*pref_name == prefs::kShowHomeButton) {
-        Layout();
-        SchedulePaint();
-      }
-      break;
-    }
     case chrome::NOTIFICATION_UPGRADE_RECOMMENDED:
     case chrome::NOTIFICATION_MODULE_INCOMPATIBILITY_BADGE_CHANGE:
     case chrome::NOTIFICATION_GLOBAL_ERRORS_CHANGED:
@@ -551,6 +543,14 @@ void ToolbarView::Observe(int type,
   }
 }
 
+void ToolbarView::OnPreferenceChanged(PrefServiceBase* service,
+                                      const std::string& pref_name) {
+  if (pref_name == prefs::kShowHomeButton) {
+    Layout();
+    SchedulePaint();
+  }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // ToolbarView, ui::AcceleratorProvider implementation:
 
diff --git a/chrome/browser/ui/views/toolbar_view.h b/chrome/browser/ui/views/toolbar_view.h
index b126f89..4e6e244 100644
--- a/chrome/browser/ui/views/toolbar_view.h
+++ b/chrome/browser/ui/views/toolbar_view.h
@@ -10,6 +10,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/command_observer.h"
 #include "chrome/browser/ui/toolbar/back_forward_menu_model.h"
@@ -39,7 +40,8 @@ class ToolbarView : public views::AccessiblePaneView,
                     public content::NotificationObserver,
                     public CommandObserver,
                     public views::ButtonListener,
-                    public views::WidgetObserver {
+                    public views::WidgetObserver,
+                    public PrefObserver {
  public:
   // The view class name.
   static const char kViewClassName[];
@@ -125,6 +127,10 @@ class ToolbarView : public views::AccessiblePaneView,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Overridden from ui::AcceleratorProvider:
   virtual bool GetAcceleratorForCommandId(
       int command_id, ui::Accelerator* accelerator) OVERRIDE;
diff --git a/chrome/browser/ui/webui/extensions/extension_settings_handler.cc b/chrome/browser/ui/webui/extensions/extension_settings_handler.cc
index 902410d..262134c 100644
--- a/chrome/browser/ui/webui/extensions/extension_settings_handler.cc
+++ b/chrome/browser/ui/webui/extensions/extension_settings_handler.cc
@@ -444,7 +444,6 @@ void ExtensionSettingsHandler::Observe(
     case chrome::NOTIFICATION_EXTENSION_UPDATE_DISABLED:
     case chrome::NOTIFICATION_EXTENSION_WARNING_CHANGED:
     case chrome::NOTIFICATION_EXTENSION_BROWSER_ACTION_VISIBILITY_CHANGED:
-    case chrome::NOTIFICATION_PREF_CHANGED:
       MaybeUpdateAfterNotification();
       break;
     default:
@@ -452,6 +451,12 @@ void ExtensionSettingsHandler::Observe(
   }
 }
 
+void ExtensionSettingsHandler::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  MaybeUpdateAfterNotification();
+}
+
 void ExtensionSettingsHandler::ExtensionUninstallAccepted() {
   DCHECK(!extension_id_prompting_.empty());
 
diff --git a/chrome/browser/ui/webui/extensions/extension_settings_handler.h b/chrome/browser/ui/webui/extensions/extension_settings_handler.h
index 50e0160..fee671e 100644
--- a/chrome/browser/ui/webui/extensions/extension_settings_handler.h
+++ b/chrome/browser/ui/webui/extensions/extension_settings_handler.h
@@ -11,6 +11,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/extensions/extension_install_ui.h"
 #include "chrome/browser/extensions/extension_uninstall_dialog.h"
 #include "chrome/browser/extensions/extension_warning_set.h"
@@ -59,6 +60,7 @@ struct ExtensionPage {
 class ExtensionSettingsHandler
     : public content::WebUIMessageHandler,
       public content::NotificationObserver,
+      public PrefObserver,
       public content::WebContentsObserver,
       public ui::SelectFileDialog::Listener,
       public ExtensionUninstallDialog::Delegate,
@@ -107,6 +109,10 @@ class ExtensionSettingsHandler
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // ExtensionUninstallDialog::Delegate implementation, used for receiving
   // notification about uninstall confirmation dialog selections.
   virtual void ExtensionUninstallAccepted() OVERRIDE;
diff --git a/chrome/browser/ui/webui/ntp/app_launcher_handler.cc b/chrome/browser/ui/webui/ntp/app_launcher_handler.cc
index 701a5e2..d701b20 100644
--- a/chrome/browser/ui/webui/ntp/app_launcher_handler.cc
+++ b/chrome/browser/ui/webui/ntp/app_launcher_handler.cc
@@ -312,13 +312,6 @@ void AppLauncherHandler::Observe(int type,
       // TODO(estade): Try to get rid of this inefficient operation.
       HandleGetApps(NULL);
       break;
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      DictionaryValue dictionary;
-      FillAppDictionary(&dictionary);
-      web_ui()->CallJavascriptFunction("ntp.appsPrefChangeCallback",
-                                       dictionary);
-      break;
-    }
     case chrome::NOTIFICATION_EXTENSION_INSTALL_ERROR: {
       CrxInstaller* crx_installer = content::Source<CrxInstaller>(source).ptr();
       if (!Profile::FromWebUI(web_ui())->IsSameProfile(
@@ -336,6 +329,14 @@ void AppLauncherHandler::Observe(int type,
   }
 }
 
+void AppLauncherHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                             const std::string& pref_name) {
+  DictionaryValue dictionary;
+  FillAppDictionary(&dictionary);
+  web_ui()->CallJavascriptFunction("ntp.appsPrefChangeCallback",
+                                   dictionary);
+}
+
 void AppLauncherHandler::FillAppDictionary(DictionaryValue* dictionary) {
   // CreateAppInfo and ClearOrdinals can change the extension prefs.
   AutoReset<bool> auto_reset(&ignore_changes_, true);
diff --git a/chrome/browser/ui/webui/ntp/app_launcher_handler.h b/chrome/browser/ui/webui/ntp/app_launcher_handler.h
index d91f6ec..9280930 100644
--- a/chrome/browser/ui/webui/ntp/app_launcher_handler.h
+++ b/chrome/browser/ui/webui/ntp/app_launcher_handler.h
@@ -9,6 +9,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/common/cancelable_request.h"
 #include "chrome/browser/extensions/extension_install_prompt.h"
 #include "chrome/browser/extensions/extension_uninstall_dialog.h"
@@ -32,7 +33,8 @@ class AppNotification;
 class AppLauncherHandler : public content::WebUIMessageHandler,
                            public ExtensionUninstallDialog::Delegate,
                            public ExtensionInstallPrompt::Delegate,
-                           public content::NotificationObserver {
+                           public content::NotificationObserver,
+                           public PrefObserver {
  public:
   explicit AppLauncherHandler(ExtensionService* extension_service);
   virtual ~AppLauncherHandler();
@@ -52,6 +54,10 @@ class AppLauncherHandler : public content::WebUIMessageHandler,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Populate the given dictionary with all installed app info.
   void FillAppDictionary(base::DictionaryValue* value);
 
diff --git a/chrome/browser/ui/webui/ntp/new_tab_ui.cc b/chrome/browser/ui/webui/ntp/new_tab_ui.cc
index bf78cd0..159a06d 100644
--- a/chrome/browser/ui/webui/ntp/new_tab_ui.cc
+++ b/chrome/browser/ui/webui/ntp/new_tab_ui.cc
@@ -249,13 +249,6 @@ void NewTabUI::Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) {
   switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {  // kShowBookmarkBar
-      StringValue attached(
-          GetProfile()->GetPrefs()->GetBoolean(prefs::kShowBookmarkBar) ?
-              "true" : "false");
-      web_ui()->CallJavascriptFunction("ntp.setBookmarkBarAttached", attached);
-      break;
-    }
 #if defined(ENABLE_THEMES)
     case chrome::NOTIFICATION_BROWSER_THEME_CHANGED: {
       InitializeCSSCaches();
@@ -288,6 +281,14 @@ void NewTabUI::Observe(int type,
   }
 }
 
+void NewTabUI::OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) {
+  StringValue attached(
+      GetProfile()->GetPrefs()->GetBoolean(prefs::kShowBookmarkBar) ?
+          "true" : "false");
+  web_ui()->CallJavascriptFunction("ntp.setBookmarkBarAttached", attached);
+}
+
 void NewTabUI::InitializeCSSCaches() {
 #if defined(ENABLE_THEMES)
   Profile* profile = GetProfile();
diff --git a/chrome/browser/ui/webui/ntp/new_tab_ui.h b/chrome/browser/ui/webui/ntp/new_tab_ui.h
index 0fd64c5..59fd481 100644
--- a/chrome/browser/ui/webui/ntp/new_tab_ui.h
+++ b/chrome/browser/ui/webui/ntp/new_tab_ui.h
@@ -10,6 +10,7 @@
 
 #include "base/gtest_prod_util.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/time.h"
 #include "base/timer.h"
 #include "chrome/browser/sessions/tab_restore_service.h"
@@ -24,7 +25,8 @@ class Profile;
 
 // The WebContents used for the New Tab page.
 class NewTabUI : public content::WebUIController,
-                 public content::NotificationObserver {
+                 public content::NotificationObserver,
+                 public PrefObserver {
  public:
   explicit NewTabUI(content::WebUI* web_ui);
   virtual ~NewTabUI();
@@ -99,10 +101,15 @@ class NewTabUI : public content::WebUIController,
  private:
   FRIEND_TEST_ALL_PREFIXES(NewTabUITest, UpdateUserPrefsVersion);
 
+  // content::NotificationObserver implementation.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Reset the CSS caches.
   void InitializeCSSCaches();
 
diff --git a/chrome/browser/ui/webui/ntp/ntp_login_handler.cc b/chrome/browser/ui/webui/ntp/ntp_login_handler.cc
index 4702fb1..476150a 100644
--- a/chrome/browser/ui/webui/ntp/ntp_login_handler.cc
+++ b/chrome/browser/ui/webui/ntp/ntp_login_handler.cc
@@ -112,15 +112,17 @@ void NTPLoginHandler::Observe(int type,
                               const content::NotificationDetails& details) {
   if (type == chrome::NOTIFICATION_PROFILE_CACHED_INFO_CHANGED) {
     UpdateLogin();
-  } else if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* name = content::Details<std::string>(details).ptr();
-    if (prefs::kGoogleServicesUsername == *name)
-      UpdateLogin();
   } else {
     NOTREACHED();
   }
 }
 
+void NTPLoginHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
+  if (prefs::kGoogleServicesUsername == pref_name)
+    UpdateLogin();
+}
+
 void NTPLoginHandler::HandleInitializeSyncLogin(const ListValue* args) {
   UpdateLogin();
 }
diff --git a/chrome/browser/ui/webui/ntp/ntp_login_handler.h b/chrome/browser/ui/webui/ntp/ntp_login_handler.h
index 331caf9e..a00b313 100644
--- a/chrome/browser/ui/webui/ntp/ntp_login_handler.h
+++ b/chrome/browser/ui/webui/ntp/ntp_login_handler.h
@@ -5,6 +5,7 @@
 #ifndef CHROME_BROWSER_UI_WEBUI_NTP_NTP_LOGIN_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_NTP_NTP_LOGIN_HANDLER_H_
 
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -16,7 +17,8 @@ class Profile;
 // username at the top of the NTP (and update itself when that changes).
 // In the future it may expand to allow users to login from the NTP.
 class NTPLoginHandler : public content::WebUIMessageHandler,
-                        public content::NotificationObserver {
+                        public content::NotificationObserver,
+                        public PrefObserver {
  public:
   NTPLoginHandler();
   virtual ~NTPLoginHandler();
@@ -29,6 +31,10 @@ class NTPLoginHandler : public content::WebUIMessageHandler,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver interface
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Returns true if the login handler should be shown in a new tab page
   // for the given |profile|. |profile| must not be NULL.
   static bool ShouldShow(Profile* profile);
diff --git a/chrome/browser/ui/webui/ntp/ntp_resource_cache.cc b/chrome/browser/ui/webui/ntp/ntp_resource_cache.cc
index 153dcfa..cdd8730 100644
--- a/chrome/browser/ui/webui/ntp/ntp_resource_cache.cc
+++ b/chrome/browser/ui/webui/ntp/ntp_resource_cache.cc
@@ -218,12 +218,6 @@ void NTPResourceCache::Observe(int type,
     new_tab_html_ = NULL;
     new_tab_incognito_css_ = NULL;
     new_tab_css_ = NULL;
-  } else if (chrome::NOTIFICATION_PREF_CHANGED == type) {
-    // A change occurred to one of the preferences we care about, so flush the
-    // cache.
-    new_tab_incognito_html_ = NULL;
-    new_tab_html_ = NULL;
-    new_tab_css_ = NULL;
   } else if (chrome::NOTIFICATION_NTP_BACKGROUND_THEME_Y_POS_CHANGED == type) {
     css_background_y_pos_ = *(content::Details<int>(details).ptr());
     if (new_tab_css_.get())
@@ -233,6 +227,15 @@ void NTPResourceCache::Observe(int type,
   }
 }
 
+void NTPResourceCache::OnPreferenceChanged(PrefServiceBase* service,
+                                           const std::string& pref_name) {
+  // A change occurred to one of the preferences we care about, so flush the
+  // cache.
+  new_tab_incognito_html_ = NULL;
+  new_tab_html_ = NULL;
+  new_tab_css_ = NULL;
+}
+
 void NTPResourceCache::CreateNewTabIncognitoHTML() {
   DictionaryValue localized_strings;
   localized_strings.SetString("title",
diff --git a/chrome/browser/ui/webui/ntp/ntp_resource_cache.h b/chrome/browser/ui/webui/ntp/ntp_resource_cache.h
index c4a57b1..8569649 100644
--- a/chrome/browser/ui/webui/ntp/ntp_resource_cache.h
+++ b/chrome/browser/ui/webui/ntp/ntp_resource_cache.h
@@ -9,6 +9,7 @@
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string16.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "content/public/browser/notification_observer.h"
@@ -27,6 +28,7 @@ class ThemeProvider;
 // This class keeps a cache of NTP resources (HTML and CSS) so we don't have to
 // regenerate them all the time.
 class NTPResourceCache : public content::NotificationObserver,
+                         public PrefObserver,
                          public ProfileKeyedService {
  public:
   explicit NTPResourceCache(Profile* profile);
@@ -40,6 +42,10 @@ class NTPResourceCache : public content::NotificationObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver interface.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Returns the CSS background-position-y style for new_tab_theme.css:
   // - |y_pos| is the vertical offset of theme image in content view.
   // - |alignment| is alignment of theme image.
diff --git a/chrome/browser/ui/webui/ntp/ntp_resource_cache_android.cc b/chrome/browser/ui/webui/ntp/ntp_resource_cache_android.cc
index 28b3dae..34214f8 100644
--- a/chrome/browser/ui/webui/ntp/ntp_resource_cache_android.cc
+++ b/chrome/browser/ui/webui/ntp/ntp_resource_cache_android.cc
@@ -56,6 +56,11 @@ void NTPResourceCache::Observe(int type,
   // No notifications necessary in Android.
 }
 
+void NTPResourceCache::OnPreferenceChanged(PrefServiceBase* service,
+                                           const std::string& pref_name) {
+  // No notifications necessary in Android.
+}
+
 void NTPResourceCache::CreateNewTabHTML() {
   // TODO(estade): these strings should be defined in their relevant handlers
   // (in GetLocalizedValues) and should have more legible names.
diff --git a/chrome/browser/ui/webui/options/browser_options_handler.cc b/chrome/browser/ui/webui/options/browser_options_handler.cc
index 8275604..47d6e35 100644
--- a/chrome/browser/ui/webui/options/browser_options_handler.cc
+++ b/chrome/browser/ui/webui/options/browser_options_handler.cc
@@ -866,32 +866,34 @@ void BrowserOptionsHandler::Observe(
   } else if (type == chrome::NOTIFICATION_LOGIN_USER_IMAGE_CHANGED) {
     UpdateAccountPicture();
 #endif
-  } else if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    if (*pref_name == prefs::kDefaultBrowserSettingEnabled) {
-      UpdateDefaultBrowserState();
-    } else if (*pref_name == prefs::kDownloadExtensionsToOpen) {
-      SetupAutoOpenFileTypes();
+  } else if (type == chrome::NOTIFICATION_PROFILE_CACHED_INFO_CHANGED) {
+    if (multiprofile_)
+      SendProfilesInfo();
+  } else {
+    NOTREACHED();
+  }
+}
+
+void BrowserOptionsHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                                const std::string& pref_name) {
+  if (pref_name == prefs::kDefaultBrowserSettingEnabled) {
+    UpdateDefaultBrowserState();
+  } else if (pref_name == prefs::kDownloadExtensionsToOpen) {
+    SetupAutoOpenFileTypes();
 #if !defined(OS_CHROMEOS)
-    } else if (proxy_prefs_.IsObserved(*pref_name)) {
-      SetupProxySettingsSection();
+  } else if (proxy_prefs_.IsObserved(pref_name)) {
+    SetupProxySettingsSection();
 #endif  // !defined(OS_CHROMEOS)
-    } else if ((*pref_name == prefs::kCloudPrintEmail) ||
-               (*pref_name == prefs::kCloudPrintProxyEnabled)) {
+  } else if ((pref_name == prefs::kCloudPrintEmail) ||
+             (pref_name == prefs::kCloudPrintProxyEnabled)) {
 #if !defined(OS_CHROMEOS)
-      if (cloud_print_connector_ui_enabled_)
-        SetupCloudPrintConnectorSection();
+    if (cloud_print_connector_ui_enabled_)
+      SetupCloudPrintConnectorSection();
 #endif
-    } else if (*pref_name == prefs::kWebKitDefaultFontSize) {
-      SetupFontSizeSelector();
-    } else if (*pref_name == prefs::kDefaultZoomLevel) {
-      SetupPageZoomSelector();
-    } else {
-      NOTREACHED();
-    }
-  } else if (type == chrome::NOTIFICATION_PROFILE_CACHED_INFO_CHANGED) {
-    if (multiprofile_)
-      SendProfilesInfo();
+  } else if (pref_name == prefs::kWebKitDefaultFontSize) {
+    SetupFontSizeSelector();
+  } else if (pref_name == prefs::kDefaultZoomLevel) {
+    SetupPageZoomSelector();
   } else {
     NOTREACHED();
   }
diff --git a/chrome/browser/ui/webui/options/browser_options_handler.h b/chrome/browser/ui/webui/options/browser_options_handler.h
index b67757a..0488e10 100644
--- a/chrome/browser/ui/webui/options/browser_options_handler.h
+++ b/chrome/browser/ui/webui/options/browser_options_handler.h
@@ -8,6 +8,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/api/sync/profile_sync_service_observer.h"
 #include "chrome/browser/printing/cloud_print/cloud_print_setup_handler.h"
@@ -35,6 +36,7 @@ namespace options {
 class BrowserOptionsHandler
     : public OptionsPageUIHandler,
       public CloudPrintSetupHandlerDelegate,
+      public PrefObserver,
       public ProfileSyncServiceObserver,
       public ui::SelectFileDialog::Listener,
       public ShellIntegration::DefaultWebClientObserver,
@@ -74,6 +76,10 @@ class BrowserOptionsHandler
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // SelectFileDialog::Listener implementation
   virtual void FileSelected(const FilePath& path,
                             int index,
diff --git a/chrome/browser/ui/webui/options/chromeos/core_chromeos_options_handler.cc b/chrome/browser/ui/webui/options/chromeos/core_chromeos_options_handler.cc
index 76f5f716..4c337674 100644
--- a/chrome/browser/ui/webui/options/chromeos/core_chromeos_options_handler.cc
+++ b/chrome/browser/ui/webui/options/chromeos/core_chromeos_options_handler.cc
@@ -200,19 +200,22 @@ void CoreChromeOSOptionsHandler::Observe(
     NotifySettingsChanged(content::Details<std::string>(details).ptr());
     return;
   }
+  ::options::CoreOptionsHandler::Observe(type, source, details);
+}
+
+void CoreChromeOSOptionsHandler::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
   // Special handling for preferences kUseSharedProxies and kProxy, the latter
   // controls the former and decides if it's managed by policy/extension.
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    const PrefService* pref_service = Profile::FromWebUI(web_ui())->GetPrefs();
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    if (content::Source<PrefService>(source).ptr() == pref_service &&
-        (proxy_prefs_.IsObserved(*pref_name) ||
-         *pref_name == prefs::kUseSharedProxies)) {
-      NotifyPrefChanged(prefs::kUseSharedProxies, prefs::kProxy);
-      return;
-    }
+  const PrefService* pref_service = Profile::FromWebUI(web_ui())->GetPrefs();
+  if (service == pref_service &&
+      (proxy_prefs_.IsObserved(pref_name) ||
+       pref_name == prefs::kUseSharedProxies)) {
+    NotifyPrefChanged(prefs::kUseSharedProxies, prefs::kProxy);
+    return;
   }
-  ::options::CoreOptionsHandler::Observe(type, source, details);
+  ::options::CoreOptionsHandler::OnPreferenceChanged(service, pref_name);
 }
 
 void CoreChromeOSOptionsHandler::NotifySettingsChanged(
diff --git a/chrome/browser/ui/webui/options/chromeos/core_chromeos_options_handler.h b/chrome/browser/ui/webui/options/chromeos/core_chromeos_options_handler.h
index 82b9298f..e14625a 100644
--- a/chrome/browser/ui/webui/options/chromeos/core_chromeos_options_handler.h
+++ b/chrome/browser/ui/webui/options/chromeos/core_chromeos_options_handler.h
@@ -8,6 +8,7 @@
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/ui/webui/options/core_options_handler.h"
 
 namespace chromeos {
@@ -37,6 +38,10 @@ class CoreChromeOSOptionsHandler : public ::options::CoreOptionsHandler {
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
  private:
   // Notifies registered JS callbacks on ChromeOS setting change.
   void NotifySettingsChanged(const std::string* setting_name);
diff --git a/chrome/browser/ui/webui/options/content_settings_handler.cc b/chrome/browser/ui/webui/options/content_settings_handler.cc
index c8ad7a6..f2565aa1 100644
--- a/chrome/browser/ui/webui/options/content_settings_handler.cc
+++ b/chrome/browser/ui/webui/options/content_settings_handler.cc
@@ -540,17 +540,6 @@ void ContentSettingsHandler::Observe(
       break;
     }
 
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      const std::string& pref_name =
-          *content::Details<std::string>(details).ptr();
-      if (pref_name == prefs::kGeolocationContentSettings)
-        UpdateGeolocationExceptionsView();
-      else if (pref_name == prefs::kPepperFlashSettingsEnabled)
-        RefreshFlashSettingsCache(false);
-
-      break;
-    }
-
     case chrome::NOTIFICATION_DESKTOP_NOTIFICATION_SETTINGS_CHANGED: {
       UpdateNotificationExceptionsView();
       break;
@@ -566,6 +555,14 @@ void ContentSettingsHandler::Observe(
   }
 }
 
+void ContentSettingsHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                                 const std::string& pref_name) {
+  if (pref_name == prefs::kGeolocationContentSettings)
+    UpdateGeolocationExceptionsView();
+  else if (pref_name == prefs::kPepperFlashSettingsEnabled)
+    RefreshFlashSettingsCache(false);
+}
+
 void ContentSettingsHandler::OnGetPermissionSettingsCompleted(
     uint32 request_id,
     bool success,
diff --git a/chrome/browser/ui/webui/options/content_settings_handler.h b/chrome/browser/ui/webui/options/content_settings_handler.h
index 63a83ae..5aa54be 100644
--- a/chrome/browser/ui/webui/options/content_settings_handler.h
+++ b/chrome/browser/ui/webui/options/content_settings_handler.h
@@ -10,6 +10,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/pepper_flash_settings_manager.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 #include "chrome/common/content_settings.h"
@@ -23,7 +24,8 @@ class ProtocolHandlerRegistry;
 namespace options {
 
 class ContentSettingsHandler : public OptionsPageUIHandler,
-                               public PepperFlashSettingsManager::Client {
+                               public PepperFlashSettingsManager::Client,
+                               public PrefObserver {
  public:
   ContentSettingsHandler();
   virtual ~ContentSettingsHandler();
@@ -40,6 +42,10 @@ class ContentSettingsHandler : public OptionsPageUIHandler,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // PepperFlashSettingsManager::Client implementation.
   virtual void OnGetPermissionSettingsCompleted(
       uint32 request_id,
diff --git a/chrome/browser/ui/webui/options/core_options_handler.cc b/chrome/browser/ui/webui/options/core_options_handler.cc
index ea50be9..8e14ea1 100644
--- a/chrome/browser/ui/webui/options/core_options_handler.cc
+++ b/chrome/browser/ui/webui/options/core_options_handler.cc
@@ -135,22 +135,18 @@ void CoreOptionsHandler::Uninitialize() {
   }
 }
 
-void CoreOptionsHandler::Observe(int type,
-                                 const content::NotificationSource& source,
-                                 const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    if (*pref_name == prefs::kClearPluginLSODataEnabled) {
-      // This preference is stored in Local State, not in the user preferences.
-      UpdateClearPluginLSOData();
-      return;
-    }
-    if (*pref_name == prefs::kPepperFlashSettingsEnabled) {
-      UpdatePepperFlashSettingsEnabled();
-      return;
-    }
-    NotifyPrefChanged(*pref_name, std::string());
+void CoreOptionsHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                             const std::string& pref_name) {
+  if (pref_name == prefs::kClearPluginLSODataEnabled) {
+    // This preference is stored in Local State, not in the user preferences.
+    UpdateClearPluginLSOData();
+    return;
+  }
+  if (pref_name == prefs::kPepperFlashSettingsEnabled) {
+    UpdatePepperFlashSettingsEnabled();
+    return;
   }
+  NotifyPrefChanged(pref_name, std::string());
 }
 
 void CoreOptionsHandler::RegisterMessages() {
diff --git a/chrome/browser/ui/webui/options/core_options_handler.h b/chrome/browser/ui/webui/options/core_options_handler.h
index aff1ee7..8cf06f5 100644
--- a/chrome/browser/ui/webui/options/core_options_handler.h
+++ b/chrome/browser/ui/webui/options/core_options_handler.h
@@ -10,6 +10,7 @@
 
 #include "base/callback.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/values.h"
 #include "chrome/browser/plugins/plugin_status_pref_setter.h"
 #include "chrome/browser/prefs/pref_service.h"
@@ -19,7 +20,8 @@ namespace options {
 
 // Core options UI handler.
 // Handles resource and JS calls common to all options sub-pages.
-class CoreOptionsHandler : public OptionsPageUIHandler {
+class CoreOptionsHandler : public OptionsPageUIHandler,
+                           public PrefObserver {
  public:
   CoreOptionsHandler();
   virtual ~CoreOptionsHandler();
@@ -30,10 +32,9 @@ class CoreOptionsHandler : public OptionsPageUIHandler {
   virtual void InitializePage() OVERRIDE;
   virtual void Uninitialize() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // WebUIMessageHandler implementation.
   virtual void RegisterMessages() OVERRIDE;
diff --git a/chrome/browser/ui/webui/options/font_settings_handler.cc b/chrome/browser/ui/webui/options/font_settings_handler.cc
index ce58d39..22f200e 100644
--- a/chrome/browser/ui/webui/options/font_settings_handler.cc
+++ b/chrome/browser/ui/webui/options/font_settings_handler.cc
@@ -187,27 +187,23 @@ void FontSettingsHandler::FontsListHasLoaded(
                                    selected_values);
 }
 
-void FontSettingsHandler::Observe(int type,
-                                  const content::NotificationSource& source,
-                                  const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    if (*pref_name == prefs::kWebKitStandardFontFamily) {
-      SetUpStandardFontSample();
-    } else if (*pref_name == prefs::kWebKitSerifFontFamily) {
-      SetUpSerifFontSample();
-    } else if (*pref_name == prefs::kWebKitSansSerifFontFamily) {
-      SetUpSansSerifFontSample();
-    } else if (*pref_name == prefs::kWebKitFixedFontFamily ||
-               *pref_name == prefs::kWebKitDefaultFixedFontSize) {
-      SetUpFixedFontSample();
-    } else if (*pref_name == prefs::kWebKitDefaultFontSize) {
-      SetUpStandardFontSample();
-      SetUpSerifFontSample();
-      SetUpSansSerifFontSample();
-    } else if (*pref_name == prefs::kWebKitMinimumFontSize) {
-      SetUpMinimumFontSample();
-    }
+void FontSettingsHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                              const std::string& pref_name) {
+  if (pref_name == prefs::kWebKitStandardFontFamily) {
+    SetUpStandardFontSample();
+  } else if (pref_name == prefs::kWebKitSerifFontFamily) {
+    SetUpSerifFontSample();
+  } else if (pref_name == prefs::kWebKitSansSerifFontFamily) {
+    SetUpSansSerifFontSample();
+  } else if (pref_name == prefs::kWebKitFixedFontFamily ||
+             pref_name == prefs::kWebKitDefaultFixedFontSize) {
+    SetUpFixedFontSample();
+  } else if (pref_name == prefs::kWebKitDefaultFontSize) {
+    SetUpStandardFontSample();
+    SetUpSerifFontSample();
+    SetUpSansSerifFontSample();
+  } else if (pref_name == prefs::kWebKitMinimumFontSize) {
+    SetUpMinimumFontSample();
   }
 }
 
diff --git a/chrome/browser/ui/webui/options/font_settings_handler.h b/chrome/browser/ui/webui/options/font_settings_handler.h
index 9b263c7..1c6af16 100644
--- a/chrome/browser/ui/webui/options/font_settings_handler.h
+++ b/chrome/browser/ui/webui/options/font_settings_handler.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_UI_WEBUI_OPTIONS_FONT_SETTINGS_HANDLER_H_
 
 #include "base/memory/scoped_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 
@@ -16,7 +17,8 @@ class ListValue;
 namespace options {
 
 // Font settings overlay page UI handler.
-class FontSettingsHandler : public OptionsPageUIHandler {
+class FontSettingsHandler : public OptionsPageUIHandler,
+                            public PrefObserver {
  public:
   FontSettingsHandler();
   virtual ~FontSettingsHandler();
@@ -28,10 +30,9 @@ class FontSettingsHandler : public OptionsPageUIHandler {
   // WebUIMessageHandler implementation.
   virtual void RegisterMessages() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   void HandleFetchFontsData(const ListValue* args);
diff --git a/chrome/browser/ui/webui/options/media_galleries_handler.cc b/chrome/browser/ui/webui/options/media_galleries_handler.cc
index 903712f..072dd7b 100644
--- a/chrome/browser/ui/webui/options/media_galleries_handler.cc
+++ b/chrome/browser/ui/webui/options/media_galleries_handler.cc
@@ -130,17 +130,10 @@ void MediaGalleriesHandler::FileSelected(
   prefs->AddGalleryByPath(path);
 }
 
-void MediaGalleriesHandler::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED &&
-      *content::Details<std::string>(details).ptr() ==
-          prefs::kMediaGalleriesRememberedGalleries) {
-    OnGalleriesChanged();
-  } else {
-    NOTREACHED();
-  }
+void MediaGalleriesHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                                const std::string& pref_name) {
+  DCHECK_EQ(std::string(prefs::kMediaGalleriesRememberedGalleries), pref_name);
+  OnGalleriesChanged();
 }
 
 }  // namespace options
diff --git a/chrome/browser/ui/webui/options/media_galleries_handler.h b/chrome/browser/ui/webui/options/media_galleries_handler.h
index 451a37d..7ce549b 100644
--- a/chrome/browser/ui/webui/options/media_galleries_handler.h
+++ b/chrome/browser/ui/webui/options/media_galleries_handler.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_UI_WEBUI_OPTIONS_MEDIA_GALLERIES_HANDLER_H_
 
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 #include "content/public/browser/notification_observer.h"
 #include "ui/base/dialogs/select_file_dialog.h"
@@ -14,6 +15,7 @@ namespace options {
 
 // Handles messages related to adding or removing media galleries.
 class MediaGalleriesHandler : public OptionsPageUIHandler,
+                              public PrefObserver,
                               public ui::SelectFileDialog::Listener {
  public:
   MediaGalleriesHandler();
@@ -28,10 +30,9 @@ class MediaGalleriesHandler : public OptionsPageUIHandler,
   virtual void FileSelected(const FilePath& path, int index, void* params)
       OVERRIDE;
 
-  // NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   // Handles the "addNewGallery" message (no arguments).
diff --git a/chrome/browser/ui/webui/options/password_manager_handler.cc b/chrome/browser/ui/webui/options/password_manager_handler.cc
index 73d6cb3..1aefb9b 100644
--- a/chrome/browser/ui/webui/options/password_manager_handler.cc
+++ b/chrome/browser/ui/webui/options/password_manager_handler.cc
@@ -109,18 +109,10 @@ PasswordStore* PasswordManagerHandler::GetPasswordStore() {
       Profile::EXPLICIT_ACCESS);
 }
 
-void PasswordManagerHandler::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    if (*pref_name == prefs::kPasswordManagerAllowShowPasswords) {
-      UpdatePasswordLists(NULL);
-    }
-  }
-
-  OptionsPageUIHandler::Observe(type, source, details);
+void PasswordManagerHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                                 const std::string& pref_name) {
+  DCHECK_EQ(std::string(prefs::kPasswordManagerAllowShowPasswords), pref_name);
+  UpdatePasswordLists(NULL);
 }
 
 void PasswordManagerHandler::UpdatePasswordLists(const ListValue* args) {
diff --git a/chrome/browser/ui/webui/options/password_manager_handler.h b/chrome/browser/ui/webui/options/password_manager_handler.h
index f7b7fc9..4a1436e 100644
--- a/chrome/browser/ui/webui/options/password_manager_handler.h
+++ b/chrome/browser/ui/webui/options/password_manager_handler.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "base/memory/scoped_vector.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/password_manager/password_store.h"
 #include "chrome/browser/password_manager/password_store_consumer.h"
@@ -21,7 +22,8 @@ struct PasswordForm;
 namespace options {
 
 class PasswordManagerHandler : public OptionsPageUIHandler,
-                               public PasswordStore::Observer {
+                               public PasswordStore::Observer,
+                               public PrefObserver {
  public:
   PasswordManagerHandler();
   virtual ~PasswordManagerHandler();
@@ -34,10 +36,9 @@ class PasswordManagerHandler : public OptionsPageUIHandler,
   // PasswordStore::Observer implementation.
   virtual void OnLoginsChanged() OVERRIDE;
 
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   // The password store associated with the currently active profile.
diff --git a/chrome/browser/ui/webui/options/preferences_browsertest.cc b/chrome/browser/ui/webui/options/preferences_browsertest.cc
index 676227d..5f31347 100644
--- a/chrome/browser/ui/webui/options/preferences_browsertest.cc
+++ b/chrome/browser/ui/webui/options/preferences_browsertest.cc
@@ -162,14 +162,10 @@ void PreferencesBrowserTest::SetUpOnMainThread() {
 }
 
 // Forwards notifications received when pref values change in the backend.
-void PreferencesBrowserTest::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  ASSERT_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  ASSERT_EQ(pref_service_, content::Source<PrefService>(source).ptr());
-  const std::string& name = *content::Details<std::string>(details).ptr();
-  OnCommit(pref_service_->FindPreference(name.c_str()));
+void PreferencesBrowserTest::OnPreferenceChanged(PrefServiceBase* service,
+                                                 const std::string& pref_name) {
+  ASSERT_EQ(pref_service_, service);
+  OnCommit(pref_service_->FindPreference(pref_name.c_str()));
 }
 
 // Sets up a mock user policy provider.
diff --git a/chrome/browser/ui/webui/options/preferences_browsertest.h b/chrome/browser/ui/webui/options/preferences_browsertest.h
index 1caa410..25d14b0 100644
--- a/chrome/browser/ui/webui/options/preferences_browsertest.h
+++ b/chrome/browser/ui/webui/options/preferences_browsertest.h
@@ -11,6 +11,7 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/policy/mock_configuration_policy_provider.h"
 #include "chrome/browser/policy/policy_types.h"
 #include "chrome/browser/prefs/pref_service.h"
@@ -33,7 +34,7 @@ class RenderViewHost;
 // CoreOptionsHandler and the specialized classes handling Chrome OS device and
 // proxy prefs behave correctly.
 class PreferencesBrowserTest : public InProcessBrowserTest,
-                               public content::NotificationObserver {
+                               public PrefObserver {
  public:
   PreferencesBrowserTest();
   ~PreferencesBrowserTest();
@@ -41,10 +42,9 @@ class PreferencesBrowserTest : public InProcessBrowserTest,
   // InProcessBrowserTest implementation:
   virtual void SetUpOnMainThread() OVERRIDE;
 
-  // content::NotificationObserver implementation:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  protected:
   MOCK_METHOD1(OnCommit, void(const PrefService::Preference*));
diff --git a/chrome/browser/ui/webui/options/startup_pages_handler.cc b/chrome/browser/ui/webui/options/startup_pages_handler.cc
index 2d2b476..9ffb34f 100644
--- a/chrome/browser/ui/webui/options/startup_pages_handler.cc
+++ b/chrome/browser/ui/webui/options/startup_pages_handler.cc
@@ -130,17 +130,10 @@ void StartupPagesHandler::OnItemsRemoved(int start, int length) {
   OnModelChanged();
 }
 
-void StartupPagesHandler::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* pref = content::Details<std::string>(details).ptr();
-    if (*pref == prefs::kURLsToRestoreOnStartup) {
-      UpdateStartupPages();
-    } else {
-      NOTREACHED();
-    }
+void StartupPagesHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                              const std::string& pref_name) {
+  if (pref_name == prefs::kURLsToRestoreOnStartup) {
+    UpdateStartupPages();
   } else {
     NOTREACHED();
   }
diff --git a/chrome/browser/ui/webui/options/startup_pages_handler.h b/chrome/browser/ui/webui/options/startup_pages_handler.h
index 98f7f23..4e9e639 100644
--- a/chrome/browser/ui/webui/options/startup_pages_handler.h
+++ b/chrome/browser/ui/webui/options/startup_pages_handler.h
@@ -9,6 +9,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/autocomplete/autocomplete_controller_delegate.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
@@ -23,6 +24,7 @@ namespace options {
 // Chrome browser options page UI handler.
 class StartupPagesHandler : public OptionsPageUIHandler,
                             public AutocompleteControllerDelegate,
+                            public PrefObserver,
                             public ui::TableModelObserver {
  public:
   StartupPagesHandler();
@@ -44,10 +46,9 @@ class StartupPagesHandler : public OptionsPageUIHandler,
   virtual void OnItemsRemoved(int start, int length) OVERRIDE;
 
  private:
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Saves the changes that have been made. Called from WebUI.
   void CommitChanges(const ListValue* args);
diff --git a/chrome/browser/ui/zoom/zoom_controller.cc b/chrome/browser/ui/zoom/zoom_controller.cc
index a706ae9..6b0de35 100644
--- a/chrome/browser/ui/zoom/zoom_controller.cc
+++ b/chrome/browser/ui/zoom/zoom_controller.cc
@@ -65,19 +65,14 @@ void ZoomController::DidNavigateMainFrame(
 void ZoomController::Observe(int type,
                              const content::NotificationSource& source,
                              const content::NotificationDetails& details) {
-  switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED: {
-      std::string* pref_name = content::Details<std::string>(details).ptr();
-      DCHECK(pref_name && *pref_name == prefs::kDefaultZoomLevel);
-      UpdateState(std::string());
-      break;
-    }
-    case content::NOTIFICATION_ZOOM_LEVEL_CHANGED:
-      UpdateState(*content::Details<std::string>(details).ptr());
-      break;
-    default:
-      NOTREACHED();
-  }
+  DCHECK_EQ(content::NOTIFICATION_ZOOM_LEVEL_CHANGED, type);
+  UpdateState(*content::Details<std::string>(details).ptr());
+}
+
+void ZoomController::OnPreferenceChanged(PrefServiceBase* service,
+                                         const std::string& pref_name) {
+  DCHECK(pref_name == prefs::kDefaultZoomLevel);
+  UpdateState(std::string());
 }
 
 void ZoomController::UpdateState(const std::string& host) {
diff --git a/chrome/browser/ui/zoom/zoom_controller.h b/chrome/browser/ui/zoom/zoom_controller.h
index ffc2a78f..f7aed95 100644
--- a/chrome/browser/ui/zoom/zoom_controller.h
+++ b/chrome/browser/ui/zoom/zoom_controller.h
@@ -7,6 +7,7 @@
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -21,6 +22,7 @@ class WebContents;
 
 // Per-tab class to manage the Omnibox zoom icon.
 class ZoomController : public content::NotificationObserver,
+                       public PrefObserver,
                        public content::WebContentsObserver,
                        public content::WebContentsUserData<ZoomController> {
  public:
@@ -50,6 +52,10 @@ class ZoomController : public content::NotificationObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver overrides:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Updates the zoom icon and zoom percentage based on current values and
   // notifies the observer if changes have occurred. |host| may be empty,
   // meaning the change should apply to ~all sites. If it is not empty, the
diff --git a/chrome/common/DEPS b/chrome/common/DEPS
index 03adafd..cefae53 100644
--- a/chrome/common/DEPS
+++ b/chrome/common/DEPS
@@ -13,7 +13,6 @@ include_rules = [
   "+webkit/user_agent",
 
   # TODO(jam): remove me once chrome_notifcation_types.h moves to browser
-  "+content/public/browser/notification_source.h",
   "+content/public/browser/notification_types.h",
 
   # Other libraries.
diff --git a/chrome/common/chrome_notification_types.h b/chrome/common/chrome_notification_types.h
index 01fed07..1245ae7 100644
--- a/chrome/common/chrome_notification_types.h
+++ b/chrome/common/chrome_notification_types.h
@@ -406,14 +406,6 @@ enum NotificationType {
   // to policy.  Source and details are unused.
   NOTIFICATION_DEFAULT_SEARCH_POLICY_CHANGED,
 
-  // This is sent to a pref observer when a pref is changed. The source is the
-  // PrefService and the details a std::string of the changed path.
-  NOTIFICATION_PREF_CHANGED,
-
-  // This is broadcast after the preference subsystem has completed
-  // asynchronous initalization of a PrefService.
-  NOTIFICATION_PREF_INITIALIZATION_COMPLETED,
-
   // The state of a web resource has been changed. A resource may have been
   // added, removed, or altered. Source is WebResourceService, and the
   // details are NoDetails.