Revert 106660 - Speculative revert. Tests are now sporadically timing out/crashing with ExtensionSettingsApiTest on the stack.

Add onChanged events to the extension settings API, both from sync and between split mode background pages.

BUG=97545
TEST=Updated ExtensionSettingsStorageUnittest, ExtensionSettingsSyncUnittest, ExtensionSettingsApitest

Review URL: http://codereview.chromium.org/8177022

TBR=kalman@chromium.org
Review URL: http://codereview.chromium.org/8365027

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@106671 0039d316-1c4b-4281-b951-d872f2087c98

26 files changed, 415 insertions, 1211 deletions

diff --git a/chrome/browser/extensions/extension_event_names.cc b/chrome/browser/extensions/extension_event_names.cc
index bc63d34..8c67a4d 100644
--- a/chrome/browser/extensions/extension_event_names.cc
+++ b/chrome/browser/extensions/extension_event_names.cc
@@ -35,6 +35,4 @@ const char kOnInputMethodChanged[] = "inputMethodPrivate.onChanged";
 const char kOnDownloadCreated[] = "experimental.downloads.onCreated";
 const char kOnDownloadChanged[] = "experimental.downloads.onChanged";
 const char kOnDownloadErased[] = "experimental.downloads.onErased";
-
-const char kOnSettingsChanged[] = "experimental.settings.onChanged";
 }  // namespace extension_event_names
diff --git a/chrome/browser/extensions/extension_event_names.h b/chrome/browser/extensions/extension_event_names.h
index 3955276..67b3dd2 100644
--- a/chrome/browser/extensions/extension_event_names.h
+++ b/chrome/browser/extensions/extension_event_names.h
@@ -45,9 +45,6 @@ extern const char kOnDownloadCreated[];
 extern const char kOnDownloadChanged[];
 extern const char kOnDownloadErased[];
 
-// Settings.
-extern const char kOnSettingsChanged[];
-
 };  // namespace extension_event_names
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_EVENT_NAMES_H_
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index 193540f2..e23bba9 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -591,7 +591,8 @@ ExtensionService::ExtensionService(Profile* profile,
     : weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)),
       profile_(profile),
       extension_prefs_(extension_prefs),
-      extension_settings_frontend_(profile),
+      extension_settings_frontend_(
+          profile->GetPath().AppendASCII(kSettingsDirectoryName)),
       pending_extension_manager_(*ALLOW_THIS_IN_INITIALIZER_LIST(this)),
       install_directory_(install_directory),
       extensions_enabled_(extensions_enabled),
diff --git a/chrome/browser/extensions/extension_setting_changes.cc b/chrome/browser/extensions/extension_setting_changes.cc
deleted file mode 100644
index ce1a95c..0000000
--- a/chrome/browser/extensions/extension_setting_changes.cc
+++ /dev/null
@@ -1,38 +0,0 @@
-// Copyright (c) 2011 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.
-
-#include "chrome/browser/extensions/extension_setting_changes.h"
-
-#include "base/json/json_writer.h"
-
-void ExtensionSettingChanges::Builder::AppendChange(
-    const std::string& key, Value* old_value, Value* new_value) {
-  DictionaryValue* change = new DictionaryValue();
-  changes_.Append(change);
-
-  change->SetString("key", key);
-  if (old_value) {
-    change->Set("oldValue", old_value);
-  }
-  if (new_value) {
-    change->Set("newValue", new_value);
-  }
-}
-
-ExtensionSettingChanges ExtensionSettingChanges::Builder::Build() {
-  return ExtensionSettingChanges(&changes_);
-}
-
-ExtensionSettingChanges::ExtensionSettingChanges(ListValue* changes)
-    : inner_(new Inner()) {
-  inner_->changes_.Swap(changes);
-}
-
-ExtensionSettingChanges::~ExtensionSettingChanges() {}
-
-std::string ExtensionSettingChanges::ToJson() const {
-  std::string changes_json;
-  base::JSONWriter::Write(&inner_->changes_, false, &changes_json);
-  return changes_json;
-}
diff --git a/chrome/browser/extensions/extension_setting_changes.h b/chrome/browser/extensions/extension_setting_changes.h
deleted file mode 100644
index af9f363..0000000
--- a/chrome/browser/extensions/extension_setting_changes.h
+++ /dev/null
@@ -1,66 +0,0 @@
-// Copyright (c) 2011 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 CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTING_CHANGES_H_
-#define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTING_CHANGES_H_
-#pragma once
-
-#include "base/memory/ref_counted.h"
-#include "base/values.h"
-
-// A list of changes to extension settings.  Create using the Builder class.
-// The Changes object is thread-safe and efficient to copy, while the Builder
-// object isn't.
-class ExtensionSettingChanges {
- public:
-  // Non-thread-safe builder for ExtensionSettingChanges.
-  class Builder {
-   public:
-    Builder() {}
-
-    // Appends a change for a setting.
-    void AppendChange(
-        const std::string& key,
-        // Ownership taken.  May be NULL to imply there is no old value.
-        Value* old_value,
-        // Ownership taken.  May be NULL to imply there is no new value.
-        Value* new_value);
-
-    // Creates an ExtensionSettingChanges object.  The Builder should not be
-    // used after calling this.
-    ExtensionSettingChanges Build();
-
-   private:
-    ListValue changes_;
-
-    DISALLOW_COPY_AND_ASSIGN(Builder);
-  };
-
-  ~ExtensionSettingChanges();
-
-  // Gets the JSON serialized form of the changes, for example:
-  // [ { "key": "foo", "oldValue": "bar", "newValue": "baz" } ]
-  std::string ToJson() const;
-
- private:
-  // Create using the Builder class.  |changes| will be cleared.
-  explicit ExtensionSettingChanges(ListValue* changes);
-
-  // Ref-counted inner class, a wrapper over a non-thread-safe string.
-  class Inner : public base::RefCountedThreadSafe<Inner> {
-   public:
-    Inner() {}
-
-    // swap() this with the changes from the Builder after construction.
-    ListValue changes_;
-
-   private:
-    virtual ~Inner() {}
-    friend class base::RefCountedThreadSafe<Inner>;
-  };
-
-  scoped_refptr<Inner> inner_;
-};
-
-#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTING_CHANGES_H_
diff --git a/chrome/browser/extensions/extension_settings_api.cc b/chrome/browser/extensions/extension_settings_api.cc
index 64526d7..5da832f 100644
--- a/chrome/browser/extensions/extension_settings_api.cc
+++ b/chrome/browser/extensions/extension_settings_api.cc
@@ -25,7 +25,7 @@ bool SettingsFunction::RunImpl() {
 void SettingsFunction::RunWithBackendOnFileThread(
     ExtensionSettingsBackend* backend) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  bool success = RunWithStorage(backend, backend->GetStorage(extension_id()));
+  bool success = RunWithStorage(backend->GetStorage(extension_id()));
   BrowserThread::PostTask(
       BrowserThread::UI,
       FROM_HERE,
@@ -33,35 +33,13 @@ void SettingsFunction::RunWithBackendOnFileThread(
 }
 
 bool SettingsFunction::UseResult(
-    ExtensionSettingsBackend* backend,
     const ExtensionSettingsStorage::Result& storage_result) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   if (storage_result.HasError()) {
     error_ = storage_result.GetError();
     return false;
   }
-
-  const DictionaryValue* settings = storage_result.GetSettings();
-  if (settings) {
-    result_.reset(settings->DeepCopy());
-  }
-
-  const std::set<std::string>* changed_keys = storage_result.GetChangedKeys();
-  if (changed_keys && !changed_keys->empty()) {
-    ExtensionSettingChanges::Builder changes;
-    for (std::set<std::string>::const_iterator it = changed_keys->begin();
-        it != changed_keys->end(); ++it) {
-      const Value* old_value = storage_result.GetOldValue(*it);
-      const Value* new_value = storage_result.GetNewValue(*it);
-      changes.AppendChange(
-          *it,
-          old_value ? old_value->DeepCopy() : NULL,
-          new_value ? new_value->DeepCopy() : NULL);
-    }
-    backend->TriggerOnSettingsChanged(
-        profile(), extension_id(), changes.Build());
-  }
-
+  DictionaryValue* settings = storage_result.GetSettings();
+  result_.reset(settings == NULL ? NULL : settings->DeepCopy());
   return true;
 }
 
@@ -80,57 +58,47 @@ static void AddAllStringValues(
 }
 
 bool GetSettingsFunction::RunWithStorage(
-    ExtensionSettingsBackend* backend,
     ExtensionSettingsStorage* storage) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   Value *input;
   EXTENSION_FUNCTION_VALIDATE(args_->Get(0, &input));
   std::string as_string;
   ListValue* as_list;
   if (input->IsType(Value::TYPE_NULL)) {
-    return UseResult(backend, storage->Get());
+    return UseResult(storage->Get());
   } else if (input->GetAsString(&as_string)) {
-    return UseResult(backend, storage->Get(as_string));
+    return UseResult(storage->Get(as_string));
   } else if (input->GetAsList(&as_list)) {
     std::vector<std::string> string_list;
     AddAllStringValues(*as_list, &string_list);
-    return UseResult(backend, storage->Get(string_list));
+    return UseResult(storage->Get(string_list));
   }
-  return UseResult(
-      backend, ExtensionSettingsStorage::Result(kUnsupportedArgumentType));
+  return UseResult(ExtensionSettingsStorage::Result(kUnsupportedArgumentType));
 }
 
 bool SetSettingsFunction::RunWithStorage(
-    ExtensionSettingsBackend* backend,
     ExtensionSettingsStorage* storage) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   DictionaryValue *input;
   EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(0, &input));
-  return UseResult(backend, storage->Set(*input));
+  return UseResult(storage->Set(*input));
 }
 
 bool RemoveSettingsFunction::RunWithStorage(
-    ExtensionSettingsBackend* backend,
     ExtensionSettingsStorage* storage) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   Value *input;
   EXTENSION_FUNCTION_VALIDATE(args_->Get(0, &input));
   std::string as_string;
   ListValue* as_list;
   if (input->GetAsString(&as_string)) {
-    return UseResult(backend, storage->Remove(as_string));
+    return UseResult(storage->Remove(as_string));
   } else if (input->GetAsList(&as_list)) {
     std::vector<std::string> string_list;
     AddAllStringValues(*as_list, &string_list);
-    return UseResult(backend, storage->Remove(string_list));
+    return UseResult(storage->Remove(string_list));
   }
-  return UseResult(
-      backend, ExtensionSettingsStorage::Result(kUnsupportedArgumentType));
+  return UseResult(ExtensionSettingsStorage::Result(kUnsupportedArgumentType));
 }
 
 bool ClearSettingsFunction::RunWithStorage(
-    ExtensionSettingsBackend* backend,
     ExtensionSettingsStorage* storage) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  return UseResult(backend, storage->Clear());
+  return UseResult(storage->Clear());
 }
diff --git a/chrome/browser/extensions/extension_settings_api.h b/chrome/browser/extensions/extension_settings_api.h
index 15f3fcb..886319b 100644
--- a/chrome/browser/extensions/extension_settings_api.h
+++ b/chrome/browser/extensions/extension_settings_api.h
@@ -21,15 +21,11 @@ class SettingsFunction : public AsyncExtensionFunction {
   //
   // Implementations should fill in args themselves, though (like RunImpl)
   // may return false to imply failure.
-  virtual bool RunWithStorage(
-      ExtensionSettingsBackend* backend,
-      ExtensionSettingsStorage* storage) = 0;
+  virtual bool RunWithStorage(ExtensionSettingsStorage* storage) = 0;
 
   // Sets error_ or result_ depending on the value of a storage Result, and
   // returns whether the Result implies success (i.e. !error).
-  bool UseResult(
-      ExtensionSettingsBackend* backend,
-      const ExtensionSettingsStorage::Result& storage_result);
+  bool UseResult(const ExtensionSettingsStorage::Result& storage_result);
 
  private:
   // Called via PostTask from RunImpl.  Calls RunWithStorage and then
@@ -42,9 +38,7 @@ class GetSettingsFunction : public SettingsFunction {
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.settings.get");
 
  protected:
-  virtual bool RunWithStorage(
-      ExtensionSettingsBackend* backend,
-      ExtensionSettingsStorage* storage) OVERRIDE;
+  virtual bool RunWithStorage(ExtensionSettingsStorage* storage) OVERRIDE;
 };
 
 class SetSettingsFunction : public SettingsFunction {
@@ -52,9 +46,7 @@ class SetSettingsFunction : public SettingsFunction {
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.settings.set");
 
  protected:
-  virtual bool RunWithStorage(
-      ExtensionSettingsBackend* backend,
-      ExtensionSettingsStorage* storage) OVERRIDE;
+  virtual bool RunWithStorage(ExtensionSettingsStorage* storage) OVERRIDE;
 };
 
 class RemoveSettingsFunction : public SettingsFunction {
@@ -62,9 +54,7 @@ class RemoveSettingsFunction : public SettingsFunction {
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.settings.remove");
 
  protected:
-  virtual bool RunWithStorage(
-      ExtensionSettingsBackend* backend,
-      ExtensionSettingsStorage* storage) OVERRIDE;
+  virtual bool RunWithStorage(ExtensionSettingsStorage* storage) OVERRIDE;
 };
 
 class ClearSettingsFunction : public SettingsFunction {
@@ -72,9 +62,7 @@ class ClearSettingsFunction : public SettingsFunction {
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.settings.clear");
 
  protected:
-  virtual bool RunWithStorage(
-      ExtensionSettingsBackend* backend,
-      ExtensionSettingsStorage* storage) OVERRIDE;
+  virtual bool RunWithStorage(ExtensionSettingsStorage* storage) OVERRIDE;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_API_H_
diff --git a/chrome/browser/extensions/extension_settings_apitest.cc b/chrome/browser/extensions/extension_settings_apitest.cc
index ad1a1fb..213d921 100644
--- a/chrome/browser/extensions/extension_settings_apitest.cc
+++ b/chrome/browser/extensions/extension_settings_apitest.cc
@@ -2,36 +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/command_line.h"
 #include "base/json/json_writer.h"
 #include "chrome/browser/extensions/extension_apitest.h"
-#include "chrome/browser/extensions/extension_service.h"
-#include "chrome/browser/extensions/extension_settings_backend.h"
-#include "chrome/browser/extensions/extension_settings_sync_util.h"
 #include "chrome/browser/extensions/extension_test_message_listener.h"
 #include "chrome/browser/profiles/profile.h"
-#include "chrome/browser/sync/api/sync_change.h"
-#include "chrome/browser/sync/api/sync_change_processor.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/test/base/ui_test_utils.h"
 
-namespace {
-
-class NoopSyncChangeProcessor : public SyncChangeProcessor {
- public:
-  virtual SyncError ProcessSyncChanges(
-      const tracked_objects::Location& from_here,
-      const SyncChangeList& change_list) OVERRIDE {
-    return SyncError();
-  }
-
-  virtual ~NoopSyncChangeProcessor() {};
-};
-
-}  // namespace
-
 class ExtensionSettingsApiTest : public ExtensionApiTest {
  protected:
   void ReplyWhenSatisfied(
@@ -41,11 +20,11 @@ class ExtensionSettingsApiTest : public ExtensionApiTest {
         normal_action, incognito_action, NULL, false);
   }
 
-  const Extension* LoadAndReplyWhenSatisfied(
+  void LoadAndReplyWhenSatisfied(
       const std::string& normal_action,
       const std::string& incognito_action,
       const std::string& extension_dir) {
-    return MaybeLoadAndReplyWhenSatisfied(
+    MaybeLoadAndReplyWhenSatisfied(
         normal_action, incognito_action, &extension_dir, false);
   }
 
@@ -55,26 +34,8 @@ class ExtensionSettingsApiTest : public ExtensionApiTest {
     MaybeLoadAndReplyWhenSatisfied(normal_action, incognito_action, NULL, true);
   }
 
-  void InitSync(SyncChangeProcessor* sync_processor) {
-    browser()->profile()->GetExtensionService()->
-        extension_settings_frontend()->RunWithBackend(base::Bind(
-            &ExtensionSettingsApiTest::InitSyncWithBackend,
-            this,
-            sync_processor));
-    MessageLoop::current()->RunAllPending();
-  }
-
-  void SendChanges(const SyncChangeList& change_list) {
-    browser()->profile()->GetExtensionService()->
-        extension_settings_frontend()->RunWithBackend(base::Bind(
-            &ExtensionSettingsApiTest::SendChangesToBackend,
-            this,
-            change_list));
-    MessageLoop::current()->RunAllPending();
-  }
-
  private:
-  const Extension* MaybeLoadAndReplyWhenSatisfied(
+  void MaybeLoadAndReplyWhenSatisfied(
       const std::string& normal_action,
       const std::string& incognito_action,
       // May be NULL to imply not loading the extension.
@@ -85,11 +46,9 @@ class ExtensionSettingsApiTest : public ExtensionApiTest {
 
     // Only load the extension after the listeners have been set up, to avoid
     // initialisation race conditions.
-    const Extension* extension = NULL;
     if (extension_dir) {
-      extension = LoadExtensionIncognito(
-          test_data_dir_.AppendASCII("settings").AppendASCII(*extension_dir));
-      EXPECT_TRUE(extension);
+      ASSERT_TRUE(LoadExtensionIncognito(test_data_dir_
+          .AppendASCII("settings").AppendASCII(*extension_dir)));
     }
 
     EXPECT_TRUE(listener.WaitUntilSatisfied());
@@ -97,7 +56,6 @@ class ExtensionSettingsApiTest : public ExtensionApiTest {
 
     listener.Reply(CreateMessage(normal_action, is_final_action));
     listener_incognito.Reply(CreateMessage(incognito_action, is_final_action));
-    return extension;
   }
 
   std::string CreateMessage(const std::string& action, bool is_final_action) {
@@ -108,19 +66,6 @@ class ExtensionSettingsApiTest : public ExtensionApiTest {
     base::JSONWriter::Write(message.get(), false, &message_json);
     return message_json;
   }
-
-  void InitSyncWithBackend(
-      SyncChangeProcessor* sync_processor, ExtensionSettingsBackend* backend) {
-    EXPECT_FALSE(backend->MergeDataAndStartSyncing(
-        syncable::EXTENSION_SETTINGS,
-        SyncDataList(),
-        sync_processor).IsSet());
-  }
-
-  void SendChangesToBackend(
-      const SyncChangeList& change_list, ExtensionSettingsBackend* backend) {
-    EXPECT_FALSE(backend->ProcessSyncChanges(FROM_HERE, change_list).IsSet());
-  }
 };
 
 IN_PROC_BROWSER_TEST_F(ExtensionSettingsApiTest, SimpleTest) {
@@ -145,93 +90,15 @@ IN_PROC_BROWSER_TEST_F(ExtensionSettingsApiTest, SplitModeIncognito) {
       browser()->profile()->GetOffTheRecordProfile());
 
   LoadAndReplyWhenSatisfied("assertEmpty", "assertEmpty", "split_incognito");
-  ReplyWhenSatisfied("noop", "setFoo");
-  ReplyWhenSatisfied("assertFoo", "assertFoo");
+  ReplyWhenSatisfied("noop", "setFoobar");
+  ReplyWhenSatisfied("assertFoobar", "assertFoobar");
   ReplyWhenSatisfied("clear", "noop");
   ReplyWhenSatisfied("assertEmpty", "assertEmpty");
-  ReplyWhenSatisfied("setFoo", "noop");
-  ReplyWhenSatisfied("assertFoo", "assertFoo");
+  ReplyWhenSatisfied("setFoobar", "noop");
+  ReplyWhenSatisfied("assertFoobar", "assertFoobar");
   ReplyWhenSatisfied("noop", "removeFoo");
   FinalReplyWhenSatisfied("assertEmpty", "assertEmpty");
 
   EXPECT_TRUE(catcher.GetNextResult()) << catcher.message();
   EXPECT_TRUE(catcher_incognito.GetNextResult()) << catcher.message();
 }
-
-IN_PROC_BROWSER_TEST_F(ExtensionSettingsApiTest,
-    OnChangedNotificationsBetweenBackgroundPages) {
-  CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableExperimentalExtensionApis);
-
-  // We need 2 ResultCatchers because we'll be running the same test in both
-  // regular and incognito mode.
-  ResultCatcher catcher, catcher_incognito;
-  catcher.RestrictToProfile(browser()->profile());
-  catcher_incognito.RestrictToProfile(
-      browser()->profile()->GetOffTheRecordProfile());
-
-  LoadAndReplyWhenSatisfied(
-      "assertNoNotifications", "assertNoNotifications", "split_incognito");
-  ReplyWhenSatisfied("noop", "setFoo");
-  ReplyWhenSatisfied("assertAddFooNotification", "assertNoNotifications");
-  ReplyWhenSatisfied("clearNotifications", "noop");
-  ReplyWhenSatisfied("removeFoo", "noop");
-  FinalReplyWhenSatisfied(
-      "assertNoNotifications", "assertDeleteFooNotification");
-
-  EXPECT_TRUE(catcher.GetNextResult()) << catcher.message();
-  EXPECT_TRUE(catcher_incognito.GetNextResult()) << catcher.message();
-}
-
-#if defined(OS_WIN)
-// Very flaky on Windows, so just disable.  crbug.com/101110
-#define MAYBE_OnChangedNotificationsFromSync \
-    DISABLED_OnChangedNotificationsFromSync
-#else
-// Possibly flaky on other platforms, though haven't observed it yet.
-#define MAYBE_OnChangedNotificationsFromSync \
-    FLAKY_OnChangedNotificationsFromSync
-#endif
-
-IN_PROC_BROWSER_TEST_F(ExtensionSettingsApiTest,
-    MAYBE_OnChangedNotificationsFromSync) {
-  CommandLine::ForCurrentProcess()->AppendSwitch(
-      switches::kEnableExperimentalExtensionApis);
-
-  // We need 2 ResultCatchers because we'll be running the same test in both
-  // regular and incognito mode.
-  ResultCatcher catcher, catcher_incognito;
-  catcher.RestrictToProfile(browser()->profile());
-  catcher_incognito.RestrictToProfile(
-      browser()->profile()->GetOffTheRecordProfile());
-
-  const Extension* extension =
-      LoadAndReplyWhenSatisfied(
-          "assertNoNotifications", "assertNoNotifications", "split_incognito");
-  const std::string& extension_id = extension->id();
-
-  NoopSyncChangeProcessor sync_processor;
-  InitSync(&sync_processor);
-
-  // Set "foo" to "bar" via sync.
-  SyncChangeList sync_changes;
-  StringValue bar("bar");
-  sync_changes.push_back(extension_settings_sync_util::CreateAdd(
-      extension_id, "foo", bar));
-  SendChanges(sync_changes);
-
-  ReplyWhenSatisfied("assertAddFooNotification", "assertAddFooNotification");
-  ReplyWhenSatisfied("clearNotifications", "clearNotifications");
-
-  // Remove "foo" via sync.
-  sync_changes.clear();
-  sync_changes.push_back(extension_settings_sync_util::CreateDelete(
-      extension_id, "foo"));
-  SendChanges(sync_changes);
-
-  FinalReplyWhenSatisfied(
-      "assertDeleteFooNotification", "assertDeleteFooNotification");
-
-  EXPECT_TRUE(catcher.GetNextResult()) << catcher.message();
-  EXPECT_TRUE(catcher_incognito.GetNextResult()) << catcher.message();
-}
diff --git a/chrome/browser/extensions/extension_settings_backend.cc b/chrome/browser/extensions/extension_settings_backend.cc
index 56bd944..ef97825 100644
--- a/chrome/browser/extensions/extension_settings_backend.cc
+++ b/chrome/browser/extensions/extension_settings_backend.cc
@@ -36,12 +36,8 @@ const size_t kMaxSettingKeys = 512;
 
 }  // namespace
 
-ExtensionSettingsBackend::ExtensionSettingsBackend(
-    const FilePath& base_path,
-    const scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >&
-        observers)
+ExtensionSettingsBackend::ExtensionSettingsBackend(const FilePath& base_path)
     : base_path_(base_path),
-      observers_(observers),
       sync_processor_(NULL) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 }
@@ -87,10 +83,7 @@ ExtensionSettingsBackend::GetOrCreateStorageWithSyncData(
 
   syncable_storage =
       linked_ptr<SyncableExtensionSettingsStorage>(
-          new SyncableExtensionSettingsStorage(
-              observers_,
-              extension_id,
-              storage));
+          new SyncableExtensionSettingsStorage(extension_id, storage));
   if (sync_processor_) {
     // TODO(kalman): do something if StartSyncing fails.
     ignore_result(syncable_storage->StartSyncing(sync_data, sync_processor_));
@@ -115,17 +108,6 @@ void ExtensionSettingsBackend::DeleteExtensionData(
   storage_objs_.erase(maybe_storage);
 }
 
-void ExtensionSettingsBackend::TriggerOnSettingsChanged(
-    Profile* profile,
-    const std::string& extension_id,
-    const ExtensionSettingChanges& changes) const {
-  observers_->Notify(
-      &ExtensionSettingsObserver::OnSettingsChanged,
-      profile,
-      extension_id,
-      changes);
-}
-
 std::set<std::string> ExtensionSettingsBackend::GetKnownExtensionIDs() const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   std::set<std::string> result;
@@ -179,7 +161,7 @@ SyncDataList ExtensionSettingsBackend::GetAllSyncData(
       continue;
     }
 
-    const DictionaryValue* settings = maybe_settings.GetSettings();
+    DictionaryValue* settings = maybe_settings.GetSettings();
     for (DictionaryValue::key_iterator key_it = settings->begin_keys();
         key_it != settings->end_keys(); ++key_it) {
       Value *value = NULL;
diff --git a/chrome/browser/extensions/extension_settings_backend.h b/chrome/browser/extensions/extension_settings_backend.h
index 81c1067..28b0e8a 100644
--- a/chrome/browser/extensions/extension_settings_backend.h
+++ b/chrome/browser/extensions/extension_settings_backend.h
@@ -10,9 +10,7 @@
 #include "base/file_path.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
-#include "base/observer_list_threadsafe.h"
 #include "base/task.h"
-#include "chrome/browser/extensions/extension_settings_observer.h"
 #include "chrome/browser/extensions/syncable_extension_settings_storage.h"
 #include "chrome/browser/sync/api/syncable_service.h"
 
@@ -21,13 +19,9 @@
 // Lives entirely on the FILE thread.
 class ExtensionSettingsBackend : public SyncableService {
  public:
-  // |base_path| is the base of the extension settings directory, so the
-  // databases will be at base_path/extension_id.
-  // |observers| is the list of observers to settings changes.
-  explicit ExtensionSettingsBackend(
-      const FilePath& base_path,
-      const scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >&
-          observers);
+  // File path is the base of the extension settings directory.
+  // The databases will be at base_path/extension_id.
+  explicit ExtensionSettingsBackend(const FilePath& base_path);
 
   virtual ~ExtensionSettingsBackend();
 
@@ -43,13 +37,6 @@ class ExtensionSettingsBackend : public SyncableService {
   // Deletes all setting data for an extension.  Call on the FILE thread.
   void DeleteExtensionData(const std::string& extension_id);
 
-  // Sends a change event to the observer list.  |profile| is the profile which
-  // generated the change.  Must be called on the FILE thread.
-  void TriggerOnSettingsChanged(
-      Profile* profile,
-      const std::string& extension_id,
-      const ExtensionSettingChanges& changes) const;
-
   // SyncableService implementation.
   virtual SyncDataList GetAllSyncData(syncable::ModelType type) const OVERRIDE;
   virtual SyncError MergeDataAndStartSyncing(
@@ -77,10 +64,6 @@ class ExtensionSettingsBackend : public SyncableService {
   // The base file path to create any leveldb databases at.
   const FilePath base_path_;
 
-  // The list of observers to settings changes.
-  const scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >
-      observers_;
-
   // A cache of ExtensionSettingsStorage objects that have already been created.
   // Ensure that there is only ever one created per extension.
   typedef std::map<std::string, linked_ptr<SyncableExtensionSettingsStorage> >
diff --git a/chrome/browser/extensions/extension_settings_frontend.cc b/chrome/browser/extensions/extension_settings_frontend.cc
index 84bfaac..4963e92 100644
--- a/chrome/browser/extensions/extension_settings_frontend.cc
+++ b/chrome/browser/extensions/extension_settings_frontend.cc
@@ -6,117 +6,20 @@
 
 #include "base/bind.h"
 #include "base/file_path.h"
-#include "chrome/browser/extensions/extension_event_names.h"
-#include "chrome/browser/extensions/extension_event_router.h"
-#include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_settings_backend.h"
-#include "chrome/browser/profiles/profile.h"
 #include "content/browser/browser_thread.h"
-#include "content/public/browser/notification_service.h"
 
-class ExtensionSettingsFrontend::DefaultObserver
-    : public ExtensionSettingsObserver {
- public:
-  explicit DefaultObserver(Profile* profile) : target_profile_(profile) {}
-  virtual ~DefaultObserver() {}
-
-  virtual void OnSettingsChanged(
-      const Profile* origin_profile,
-      const std::string& extension_id,
-      const ExtensionSettingChanges& changes) OVERRIDE {
-    if (origin_profile != target_profile_) {
-      target_profile_->GetExtensionEventRouter()->DispatchEventToExtension(
-        extension_id,
-        extension_event_names::kOnSettingsChanged,
-        // This is the list of function arguments to pass to the onChanged
-        // handler of extensions, a single argument with the list of changes.
-        std::string("[") + changes.ToJson() + "]",
-        target_profile_,
-        GURL());
-    }
-  }
-
- private:
-  Profile* target_profile_;
-};
-
-class ExtensionSettingsFrontend::Core
-    : public base::RefCountedThreadSafe<Core> {
- public:
-  explicit Core(
-      const scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >&
-          observers)
-      : observers_(observers), backend_(NULL) {
-    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  }
-
-  // Does any FILE thread specific initialization, such as construction of
-  // |backend_|.  Must be called before any call to
-  // RunWithBackendOnFileThread().
-  void InitOnFileThread(const FilePath& base_path) {
-    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-    DCHECK(!backend_);
-    backend_ = new ExtensionSettingsBackend(base_path, observers_);
-  }
-
-  // Runs |callback| with the extension backend.
-  void RunWithBackendOnFileThread(const BackendCallback& callback) {
-    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-    DCHECK(backend_);
-    callback.Run(backend_);
-  }
-
- private:
-  virtual ~Core() {
-    if (BrowserThread::CurrentlyOn(BrowserThread::FILE)) {
-      delete backend_;
-    } else if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
-      BrowserThread::DeleteSoon(BrowserThread::FILE, FROM_HERE, backend_);
-    } else {
-      NOTREACHED();
-    }
-  }
-
-  friend class base::RefCountedThreadSafe<Core>;
-
-  // Observers to settings changes (thread safe).
-  scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >
-      observers_;
-
-  // Lives on the FILE thread.
-  ExtensionSettingsBackend* backend_;
-
-  DISALLOW_COPY_AND_ASSIGN(Core);
-};
-
-ExtensionSettingsFrontend::ExtensionSettingsFrontend(Profile* profile)
-    : profile_(profile),
-      observers_(new ObserverListThreadSafe<ExtensionSettingsObserver>()),
-      core_(new ExtensionSettingsFrontend::Core(observers_.get())) {
+ExtensionSettingsFrontend::ExtensionSettingsFrontend(
+    const FilePath& base_path)
+    : core_(new ExtensionSettingsFrontend::Core()) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK(!profile->IsOffTheRecord());
-
-  // This class listens to all PROFILE_{CREATED,DESTROYED} events but we're
-  // only interested in those for the original Profile given on construction
-  // and its incognito version.
-  registrar_.Add(this, chrome::NOTIFICATION_PROFILE_CREATED,
-      content::NotificationService::AllBrowserContextsAndSources());
-  registrar_.Add(this, chrome::NOTIFICATION_PROFILE_DESTROYED,
-      content::NotificationService::AllBrowserContextsAndSources());
-  OnProfileCreated(profile);
-
   BrowserThread::PostTask(
       BrowserThread::FILE,
       FROM_HERE,
       base::Bind(
           &ExtensionSettingsFrontend::Core::InitOnFileThread,
           core_.get(),
-          profile->GetPath().AppendASCII(
-              ExtensionService::kSettingsDirectoryName)));
-}
-
-ExtensionSettingsFrontend::~ExtensionSettingsFrontend() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+          base_path));
 }
 
 void ExtensionSettingsFrontend::RunWithBackend(
@@ -131,66 +34,34 @@ void ExtensionSettingsFrontend::RunWithBackend(
           callback));
 }
 
-void ExtensionSettingsFrontend::AddObserver(
-    ExtensionSettingsObserver* observer) {
-  observers_->AddObserver(observer);
-}
-
-void ExtensionSettingsFrontend::RemoveObserver(
-    ExtensionSettingsObserver* observer) {
-  observers_->RemoveObserver(observer);
-}
-
-void ExtensionSettingsFrontend::Observe(
-      int type,
-      const content::NotificationSource& source,
-      const content::NotificationDetails& details) {
+ExtensionSettingsFrontend::~ExtensionSettingsFrontend() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  switch (type) {
-    case chrome::NOTIFICATION_PROFILE_CREATED:
-      OnProfileCreated(content::Source<Profile>(source).ptr());
-      break;
-    case chrome::NOTIFICATION_PROFILE_DESTROYED:
-      OnProfileDestroyed(content::Source<Profile>(source).ptr());
-      break;
-    default:
-      NOTREACHED();
-  }
 }
 
-void ExtensionSettingsFrontend::OnProfileCreated(Profile* new_profile) {
+ExtensionSettingsFrontend::Core::Core() : backend_(NULL) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  if (new_profile == profile_) {
-    ClearDefaultObserver(&original_profile_observer);
-    SetDefaultObserver(new_profile, &original_profile_observer);
-  } else if (new_profile->GetOriginalProfile() == profile_) {
-    DCHECK(new_profile->IsOffTheRecord());
-    ClearDefaultObserver(&incognito_profile_observer_);
-    SetDefaultObserver(new_profile, &incognito_profile_observer_);
-  }
 }
 
-void ExtensionSettingsFrontend::OnProfileDestroyed(Profile* old_profile) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  if (old_profile == profile_) {
-    ClearDefaultObserver(&original_profile_observer);
-  } else if (old_profile->GetOriginalProfile() == profile_) {
-    DCHECK(old_profile->IsOffTheRecord());
-    ClearDefaultObserver(&incognito_profile_observer_);
-  }
+void ExtensionSettingsFrontend::Core::InitOnFileThread(
+    const FilePath& base_path) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(!backend_);
+  backend_ = new ExtensionSettingsBackend(base_path);
 }
 
-void ExtensionSettingsFrontend::SetDefaultObserver(
-    Profile* profile, scoped_ptr<DefaultObserver>* observer) {
-  DCHECK(!observer->get());
-  observer->reset(new DefaultObserver(profile));
-  AddObserver(observer->get());
+void ExtensionSettingsFrontend::Core::RunWithBackendOnFileThread(
+    const BackendCallback& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(backend_);
+  callback.Run(backend_);
 }
 
-void ExtensionSettingsFrontend::ClearDefaultObserver(
-    scoped_ptr<DefaultObserver>* observer) {
-  if (observer->get()) {
-    RemoveObserver(observer->get());
-    observer->reset();
+ExtensionSettingsFrontend::Core::~Core() {
+  if (BrowserThread::CurrentlyOn(BrowserThread::FILE)) {
+    delete backend_;
+  } else if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+    BrowserThread::DeleteSoon(BrowserThread::FILE, FROM_HERE, backend_);
+  } else {
+    NOTREACHED();
   }
 }
diff --git a/chrome/browser/extensions/extension_settings_frontend.h b/chrome/browser/extensions/extension_settings_frontend.h
index 104da18..7fe3dc0 100644
--- a/chrome/browser/extensions/extension_settings_frontend.h
+++ b/chrome/browser/extensions/extension_settings_frontend.h
@@ -6,83 +6,56 @@
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_FRONTEND_H_
 #pragma once
 
-#include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/observer_list_threadsafe.h"
-#include "chrome/browser/extensions/extension_settings_observer.h"
+#include "base/callback.h"
 #include "chrome/browser/sync/api/syncable_service.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
 
 class FilePath;
-class Profile;
 class ExtensionSettingsBackend;
 class ExtensionSettingsStorage;
 
 // The component of extension settings which runs on the UI thread, as opposed
 // to ExtensionSettingsBackend which lives on the FILE thread.
-class ExtensionSettingsFrontend : public content::NotificationObserver {
+class ExtensionSettingsFrontend {
  public:
-  explicit ExtensionSettingsFrontend(Profile* profile);
-  virtual ~ExtensionSettingsFrontend();
+  explicit ExtensionSettingsFrontend(const FilePath& base_path);
 
   typedef base::Callback<void(ExtensionSettingsBackend*)> BackendCallback;
 
   // Runs |callback| on the FILE thread with the extension settings.
   void RunWithBackend(const BackendCallback& callback);
 
-  // Adds an observer to settings changes.
-  void AddObserver(ExtensionSettingsObserver* observer);
-
-  // Removes an observer to settings changes.
-  void RemoveObserver(ExtensionSettingsObserver* observer);
-
-  // NotificationObserver implementation.
-  virtual void Observe(
-      int type,
-      const content::NotificationSource& source,
-      const content::NotificationDetails& details) OVERRIDE;
+  ~ExtensionSettingsFrontend();
 
  private:
-  // Observer which sends events to a target profile iff the profile isn't the
-  // originating profile for the event.
-  class DefaultObserver;
-
-  // Called when a profile is created.
-  void OnProfileCreated(Profile* profile);
-
-  // Called when a profile is destroyed.
-  void OnProfileDestroyed(Profile* profile);
+  // Ref-counted container for the ExtensionSettingsBackend object.
+  class Core : public base::RefCountedThreadSafe<Core> {
+   public:
+    // Constructed on UI thread.
+    Core();
 
-  // Creates a scoped DefaultObserver and adds it as an Observer.
-  void SetDefaultObserver(
-      Profile* profile, scoped_ptr<DefaultObserver>* observer);
+    // Does any FILE thread specific initialization, such as construction of
+    // |backend_|.  Must be called before any call to
+    // RunWithBackendOnFileThread().
+    void InitOnFileThread(const FilePath& base_path);
 
-  // If a scoped DefaultObserver exists, clears it and removes it as an
-  // Observer.
-  void ClearDefaultObserver(scoped_ptr<DefaultObserver>* observer);
+    // Runs |callback| with the extension backend.
+    void RunWithBackendOnFileThread(const BackendCallback& callback);
 
-  // The (original) Profile this Frontend belongs to.  Note that we don't store
-  // the incognito version of the profile because it will change as it's
-  // created and destroyed during the lifetime of Chrome.
-  Profile* const profile_;
+   private:
+    // Can be destroyed on either the UI or FILE thread.
+    virtual ~Core();
+    friend class base::RefCountedThreadSafe<Core>;
 
-  // List of observers to settings changes.
-  scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> > observers_;
+    // Lives on the FILE thread.
+    ExtensionSettingsBackend* backend_;
 
-  // The default original and incognito mode profile observers.
-  scoped_ptr<DefaultObserver> original_profile_observer;
-  scoped_ptr<DefaultObserver> incognito_profile_observer_;
+    DISALLOW_COPY_AND_ASSIGN(Core);
+  };
 
-  // Ref-counted container for the ExtensionSettingsBackend object.
-  class Core;
   scoped_refptr<Core> core_;
 
-  // For profile created/destroyed notifications.
-  content::NotificationRegistrar registrar_;
-
   DISALLOW_COPY_AND_ASSIGN(ExtensionSettingsFrontend);
 };
 
diff --git a/chrome/browser/extensions/extension_settings_frontend_unittest.cc b/chrome/browser/extensions/extension_settings_frontend_unittest.cc
index d245850..076eda3 100644
--- a/chrome/browser/extensions/extension_settings_frontend_unittest.cc
+++ b/chrome/browser/extensions/extension_settings_frontend_unittest.cc
@@ -23,13 +23,13 @@ class ExtensionSettingsFrontendTest : public testing::Test {
 
   virtual void SetUp() OVERRIDE {
     ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
+    frontend_.reset(new ExtensionSettingsFrontend(temp_dir_.path()));
     profile_.reset(new TestingProfile(temp_dir_.path()));
-    frontend_.reset(new ExtensionSettingsFrontend(profile_.get()));
   }
 
   virtual void TearDown() OVERRIDE {
-    frontend_.reset();
     profile_.reset();
+    frontend_.reset();
   }
 
  protected:
@@ -45,8 +45,8 @@ class ExtensionSettingsFrontendTest : public testing::Test {
   }
 
   ScopedTempDir temp_dir_;
-  scoped_ptr<TestingProfile> profile_;
   scoped_ptr<ExtensionSettingsFrontend> frontend_;
+  scoped_ptr<TestingProfile> profile_;
 
  private:
   // Intended as a ExtensionSettingsFrontend::BackendCallback from GetBackend.
@@ -77,7 +77,7 @@ TEST_F(ExtensionSettingsFrontendTest, SettingsPreservedAcrossReconstruction) {
   ASSERT_FALSE(result.HasError());
   EXPECT_FALSE(result.GetSettings()->empty());
 
-  frontend_.reset(new ExtensionSettingsFrontend(profile_.get()));
+  frontend_.reset(new ExtensionSettingsFrontend(temp_dir_.path()));
   GetBackend(&backend);
   storage = backend->GetStorage(id);
 
diff --git a/chrome/browser/extensions/extension_settings_leveldb_storage.cc b/chrome/browser/extensions/extension_settings_leveldb_storage.cc
index 647c232..5c86c02 100644
--- a/chrome/browser/extensions/extension_settings_leveldb_storage.cc
+++ b/chrome/browser/extensions/extension_settings_leveldb_storage.cc
@@ -100,7 +100,7 @@ ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Get(
   if (setting.get()) {
     settings->SetWithoutPathExpansion(key, setting.release());
   }
-  return Result(settings, NULL, NULL);
+  return Result(settings, NULL);
 }
 
 ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Get(
@@ -124,7 +124,7 @@ ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Get(
     }
   }
 
-  return Result(settings.release(), NULL, NULL);
+  return Result(settings.release(), NULL);
 }
 
 ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Get() {
@@ -154,7 +154,7 @@ ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Get() {
     return Result(kGenericOnFailureMessage);
   }
 
-  return Result(settings.release(), NULL, NULL);
+  return Result(settings.release(), NULL);
 }
 
 ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Set(
@@ -168,29 +168,24 @@ ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Set(
 ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Set(
     const DictionaryValue& settings) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  scoped_ptr<DictionaryValue> old_settings(new DictionaryValue());
   scoped_ptr<std::set<std::string> > changed_keys(new std::set<std::string>());
   std::string value_as_json;
   leveldb::WriteBatch batch;
 
   for (DictionaryValue::key_iterator it = settings.begin_keys();
       it != settings.end_keys(); ++it) {
-    scoped_ptr<Value> old_value;
-    if (!ReadFromDb(leveldb::ReadOptions(), *it, &old_value)) {
+    scoped_ptr<Value> original_value;
+    if (!ReadFromDb(leveldb::ReadOptions(), *it, &original_value)) {
       return Result(kGenericOnFailureMessage);
     }
 
     Value* new_value = NULL;
     settings.GetWithoutPathExpansion(*it, &new_value);
-    if (!old_value.get() || !old_value->Equals(new_value)) {
+    if (!original_value.get() || !original_value->Equals(new_value)) {
       changed_keys->insert(*it);
       base::JSONWriter::Write(new_value, false, &value_as_json);
       batch.Put(*it, value_as_json);
     }
-
-    if (old_value.get()) {
-      old_settings->SetWithoutPathExpansion(*it, old_value.release());
-    }
   }
 
   leveldb::Status status = db_->Write(leveldb::WriteOptions(), &batch);
@@ -199,8 +194,7 @@ ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Set(
     return Result(kGenericOnFailureMessage);
   }
 
-  return Result(
-      settings.DeepCopy(), old_settings.release(), changed_keys.release());
+  return Result(settings.DeepCopy(), changed_keys.release());
 }
 
 ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Remove(
@@ -214,20 +208,18 @@ ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Remove(
 ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Remove(
     const std::vector<std::string>& keys) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  scoped_ptr<DictionaryValue> old_settings(new DictionaryValue());
   scoped_ptr<std::set<std::string> > changed_keys(new std::set<std::string>());
 
   leveldb::WriteBatch batch;
   for (std::vector<std::string>::const_iterator it = keys.begin();
       it != keys.end(); ++it) {
-    scoped_ptr<Value> old_value;
-    if (!ReadFromDb(leveldb::ReadOptions(), *it, &old_value)) {
+    scoped_ptr<Value> original_value;
+    if (!ReadFromDb(leveldb::ReadOptions(), *it, &original_value)) {
       return Result(kGenericOnFailureMessage);
     }
 
-    if (old_value.get()) {
+    if (original_value.get()) {
       changed_keys->insert(*it);
-      old_settings->SetWithoutPathExpansion(*it, old_value.release());
       batch.Delete(*it);
     }
   }
@@ -238,12 +230,11 @@ ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Remove(
     return Result(kGenericOnFailureMessage);
   }
 
-  return Result(NULL, old_settings.release(), changed_keys.release());
+  return Result(NULL, changed_keys.release());
 }
 
 ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Clear() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  scoped_ptr<DictionaryValue> old_settings(new DictionaryValue());
   scoped_ptr<std::set<std::string> > changed_keys(new std::set<std::string>());
   leveldb::ReadOptions options;
   // All interaction with the db is done on the same thread, so snapshotting
@@ -254,17 +245,8 @@ ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Clear() {
   options.snapshot = snapshot.get();
   scoped_ptr<leveldb::Iterator> it(db_->NewIterator(options));
   for (it->SeekToFirst(); it->Valid(); it->Next()) {
-    const std::string key = it->key().ToString();
-    const std::string old_value_as_json = it->value().ToString();
-    changed_keys->insert(key);
-    Value* old_value =
-        base::JSONReader().JsonToValue(old_value_as_json, false, false);
-    if (old_value) {
-      old_settings->SetWithoutPathExpansion(key, old_value);
-    } else {
-      LOG(ERROR) << "Invalid JSON in database: " << old_value_as_json;
-    }
-    batch.Delete(key);
+    changed_keys->insert(it->key().ToString());
+    batch.Delete(it->key());
   }
 
   if (!it->status().ok()) {
@@ -278,7 +260,7 @@ ExtensionSettingsStorage::Result ExtensionSettingsLeveldbStorage::Clear() {
     return Result(kGenericOnFailureMessage);
   }
 
-  return Result(NULL, old_settings.release(), changed_keys.release());
+  return Result(NULL, changed_keys.release());
 }
 
 bool ExtensionSettingsLeveldbStorage::ReadFromDb(
diff --git a/chrome/browser/extensions/extension_settings_observer.cc b/chrome/browser/extensions/extension_settings_observer.cc
deleted file mode 100644
index d25ae17..0000000
--- a/chrome/browser/extensions/extension_settings_observer.cc
+++ /dev/null
@@ -1,7 +0,0 @@
-// Copyright (c) 2011 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.
-
-#include "chrome/browser/extensions/extension_settings_observer.h"
-
-ExtensionSettingsObserver::~ExtensionSettingsObserver() {}
diff --git a/chrome/browser/extensions/extension_settings_observer.h b/chrome/browser/extensions/extension_settings_observer.h
deleted file mode 100644
index 7cc2461..0000000
--- a/chrome/browser/extensions/extension_settings_observer.h
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright (c) 2011 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 CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_OBSERVER_H_
-#define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_OBSERVER_H_
-#pragma once
-
-#include "chrome/browser/extensions/extension_setting_changes.h"
-
-class Profile;
-
-// Interface for classes that listen to changes to extension settings.
-class ExtensionSettingsObserver {
- public:
-  // Called when a list of settings have changed for an extension.
-  //
-  // |profile| is the profile of the event originator, or NULL if the event
-  // didn't originate from a background page.  This is so that events can avoid
-  // being sent back to the background page which made the change.  When the
-  // settings API is exposed to content scripts, this will need to be changed.
-  virtual void OnSettingsChanged(
-      const Profile* profile,
-      const std::string& extension_id,
-      const ExtensionSettingChanges& changes) = 0;
-
- protected:
-  virtual ~ExtensionSettingsObserver();
-};
-
-#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_OBSERVER_H_
diff --git a/chrome/browser/extensions/extension_settings_storage.cc b/chrome/browser/extensions/extension_settings_storage.cc
index 3259748..882efe8 100644
--- a/chrome/browser/extensions/extension_settings_storage.cc
+++ b/chrome/browser/extensions/extension_settings_storage.cc
@@ -8,57 +8,27 @@
 // Implementation of ExtensionSettingsStorage::Result
 
 ExtensionSettingsStorage::Result::Result(
-    DictionaryValue* settings,
-    DictionaryValue* old_settings,
-    std::set<std::string>* changed_keys)
-    : inner_(new Inner(settings, old_settings, changed_keys, std::string())) {}
+    DictionaryValue* settings, std::set<std::string>* changed_keys)
+    : inner_(new Inner(settings, changed_keys, std::string())) {}
 
 ExtensionSettingsStorage::Result::Result(const std::string& error)
-    : inner_(new Inner(NULL, NULL, new std::set<std::string>(), error)) {
+    : inner_(new Inner(NULL, new std::set<std::string>(), error)) {
   DCHECK(!error.empty());
 }
 
 ExtensionSettingsStorage::Result::~Result() {}
 
-const DictionaryValue* ExtensionSettingsStorage::Result::GetSettings() const {
+DictionaryValue* ExtensionSettingsStorage::Result::GetSettings() const {
   DCHECK(!HasError());
   return inner_->settings_.get();
 }
 
-const std::set<std::string>*
+std::set<std::string>*
 ExtensionSettingsStorage::Result::GetChangedKeys() const {
   DCHECK(!HasError());
   return inner_->changed_keys_.get();
 }
 
-const Value* ExtensionSettingsStorage::Result::GetOldValue(
-    const std::string& key) const {
-  DCHECK(!HasError());
-  if (!inner_->changed_keys_.get()) {
-    return NULL;
-  }
-  Value* old_value = NULL;
-  if (inner_->changed_keys_->count(key)) {
-    inner_->old_settings_->GetWithoutPathExpansion(key, &old_value);
-  } else if (inner_->settings_.get()) {
-    inner_->settings_->GetWithoutPathExpansion(key, &old_value);
-  }
-  return old_value;
-}
-
-const Value* ExtensionSettingsStorage::Result::GetNewValue(
-    const std::string& key) const {
-  DCHECK(!HasError());
-  if (!inner_->changed_keys_.get()) {
-    return NULL;
-  }
-  Value* new_value = NULL;
-  if (inner_->settings_.get()) {
-    inner_->settings_->GetWithoutPathExpansion(key, &new_value);
-  }
-  return new_value;
-}
-
 bool ExtensionSettingsStorage::Result::HasError() const {
   return !inner_->error_.empty();
 }
@@ -70,12 +40,8 @@ const std::string& ExtensionSettingsStorage::Result::GetError() const {
 
 ExtensionSettingsStorage::Result::Inner::Inner(
     DictionaryValue* settings,
-    DictionaryValue* old_settings,
     std::set<std::string>* changed_keys,
     const std::string& error)
-    : settings_(settings),
-      old_settings_(old_settings),
-      changed_keys_(changed_keys),
-      error_(error) {}
+    : settings_(settings), changed_keys_(changed_keys), error_(error) {}
 
 ExtensionSettingsStorage::Result::Inner::~Inner() {}
diff --git a/chrome/browser/extensions/extension_settings_storage.h b/chrome/browser/extensions/extension_settings_storage.h
index 106f8fb..ba728bc 100644
--- a/chrome/browser/extensions/extension_settings_storage.h
+++ b/chrome/browser/extensions/extension_settings_storage.h
@@ -23,37 +23,25 @@ class ExtensionSettingsStorage {
   // Supports lightweight copying.
   class Result {
    public:
-    // Ownership of all arguments are taken.
+    // Ownership of |settings| and |changed_keys| taken.
     // |settings| may be NULL when the result is for an operation which
     // generates no setting values (e.g. Remove(), Clear()).
-    // |changed_keys| and |old_settings| may be NULL when the result is for an
-    // operation which cannot change settings (e.g. Get()).
-    Result(
-        DictionaryValue* settings,
-        DictionaryValue* old_settings,
-        std::set<std::string>* changed_keys);
+    // |changed_keys| may be NULL when the result is for an operation which
+    // cannot change settings (e.g. Get()).
+    Result(DictionaryValue* settings, std::set<std::string>* changed_keys);
     explicit Result(const std::string& error);
     ~Result();
 
     // The dictionary result of the computation.  NULL does not imply invalid;
     // HasError() should be used to test this.
-    // Ownership remains with this.
-    const DictionaryValue* GetSettings() const;
+    // Ownership remains with with the Result.
+    DictionaryValue* GetSettings() const;
 
-    // Gets the set of setting keys which changed as a result of the
+    // Gets the list of setting keys which changed as a result of the
     // computation.  This includes all settings that existed and removed, all
-    // settings which changed when set, and all setting keys cleared.  May be
-    // NULL for operations which cannot change settings, such as Get().
-    const std::set<std::string>* GetChangedKeys() const;
-
-    // Gets the value of a setting prior to the operation which generated
-    // this Result, or NULL if the setting had no original value or this Result
-    // is from an operation that didn't modify the settings (such as Get()).
-    // Ownerships remains with this.
-    const Value* GetOldValue(const std::string& key) const;
-
-    // Like GetOldValue, but gets the new value.
-    const Value* GetNewValue(const std::string& key) const;
+    // settings which changed when set, and all setting keys cleared.
+    // May be NULL for operations which cannot change settings, such as Get().
+    std::set<std::string>* GetChangedKeys() const;
 
     // Whether there was an error in the computation.  If so, the results of
     // GetSettings and ReleaseSettings are not valid.
@@ -67,13 +55,11 @@ class ExtensionSettingsStorage {
       // Empty error implies no error.
       Inner(
           DictionaryValue* settings,
-          DictionaryValue* old_settings,
           std::set<std::string>* changed_keys,
           const std::string& error);
       ~Inner();
 
       const scoped_ptr<DictionaryValue> settings_;
-      const scoped_ptr<DictionaryValue> old_settings_;
       const scoped_ptr<std::set<std::string> > changed_keys_;
       const std::string error_;
     };
diff --git a/chrome/browser/extensions/extension_settings_storage_cache.cc b/chrome/browser/extensions/extension_settings_storage_cache.cc
index 2df99ed..f20f068 100644
--- a/chrome/browser/extensions/extension_settings_storage_cache.cc
+++ b/chrome/browser/extensions/extension_settings_storage_cache.cc
@@ -15,7 +15,7 @@ ExtensionSettingsStorage::Result ExtensionSettingsStorageCache::Get(
   if (GetFromCache(key, &value)) {
     DictionaryValue* settings = new DictionaryValue();
     settings->SetWithoutPathExpansion(key, value);
-    return Result(settings, NULL, NULL);
+    return Result(settings, NULL);
   }
 
   Result result = delegate_->Get(key);
@@ -43,7 +43,7 @@ ExtensionSettingsStorage::Result ExtensionSettingsStorageCache::Get(
   }
 
   if (missing_keys.empty()) {
-    return Result(from_cache.release(), NULL, NULL);
+    return Result(from_cache.release(), NULL);
   }
 
   Result result = delegate_->Get(keys);
@@ -52,10 +52,8 @@ ExtensionSettingsStorage::Result ExtensionSettingsStorageCache::Get(
   }
 
   cache_.MergeDictionary(result.GetSettings());
-
-  DictionaryValue* settings_with_cache = result.GetSettings()->DeepCopy();
-  settings_with_cache->MergeDictionary(from_cache.get());
-  return Result(settings_with_cache, NULL, NULL);
+  result.GetSettings()->MergeDictionary(from_cache.get());
+  return result;
 }
 
 ExtensionSettingsStorage::Result ExtensionSettingsStorageCache::Get() {
@@ -82,9 +80,9 @@ ExtensionSettingsStorage::Result ExtensionSettingsStorageCache::Set(
     return result;
   }
 
-  const std::set<std::string>* changed_keys = result.GetChangedKeys();
+  std::set<std::string>* changed_keys = result.GetChangedKeys();
   DCHECK(changed_keys);
-  for (std::set<std::string>::const_iterator it = changed_keys->begin();
+  for (std::set<std::string>::iterator it = changed_keys->begin();
       it != changed_keys->end(); ++it) {
     Value* new_value = NULL;
     result.GetSettings()->GetWithoutPathExpansion(*it, &new_value);
@@ -110,9 +108,9 @@ ExtensionSettingsStorage::Result ExtensionSettingsStorageCache::Remove(
     return result;
   }
 
-  const std::set<std::string>* changed_keys = result.GetChangedKeys();
+  std::set<std::string>* changed_keys = result.GetChangedKeys();
   DCHECK(changed_keys);
-  for (std::set<std::string>::const_iterator it = changed_keys->begin();
+  for (std::set<std::string>::iterator it = changed_keys->begin();
       it != changed_keys->end(); ++it) {
     cache_.RemoveWithoutPathExpansion(*it, NULL);
   }
diff --git a/chrome/browser/extensions/extension_settings_storage_quota_enforcer.cc b/chrome/browser/extensions/extension_settings_storage_quota_enforcer.cc
index 6186c87..91a62ce 100644
--- a/chrome/browser/extensions/extension_settings_storage_quota_enforcer.cc
+++ b/chrome/browser/extensions/extension_settings_storage_quota_enforcer.cc
@@ -90,8 +90,7 @@ ExtensionSettingsStorageQuotaEnforcer::ExtensionSettingsStorageQuotaEnforcer(
     return;
   }
 
-  const DictionaryValue* initial_settings =
-      maybe_initial_settings.GetSettings();
+  DictionaryValue* initial_settings = maybe_initial_settings.GetSettings();
   for (DictionaryValue::key_iterator it = initial_settings->begin_keys();
       it != initial_settings->end_keys(); ++it) {
     Value *value;
diff --git a/chrome/browser/extensions/extension_settings_storage_unittest.cc b/chrome/browser/extensions/extension_settings_storage_unittest.cc
index f3080ac..a36bed9 100644
--- a/chrome/browser/extensions/extension_settings_storage_unittest.cc
+++ b/chrome/browser/extensions/extension_settings_storage_unittest.cc
@@ -33,86 +33,48 @@ std::string ToString(const std::set<std::string>& strings) {
 
 }  // namespace
 
-// Compares two possibly NULL values for equality, filling |error| with an
-// appropriate error message if they're different.
-bool ValuesEqual(
-    const Value* expected, const Value* actual, std::string* error) {
-  if (expected == actual) {
-    return true;
-  }
-  if (expected && !actual) {
-    *error = "Expected: " + GetJSON(*expected) + ", actual: NULL";
-    return false;
-  }
-  if (actual && !expected) {
-    *error = "Expected: NULL, actual: " + GetJSON(*actual);
-    return false;
-  }
-  if (!expected->Equals(actual)) {
-    *error =
-        "Expected: " + GetJSON(*expected) + ", actual: " + GetJSON(*actual);
-    return false;
-  }
-  return true;
-}
-
 // Returns whether the result of a storage operation has the expected settings
 // and changed keys.
 testing::AssertionResult SettingsEq(
-    const char* _1, const char* _2, const char* _3, const char* _4,
+    const char* _1, const char* _2, const char* _3,
     DictionaryValue* expected_settings,
-    DictionaryValue* expected_old_settings,
     std::set<std::string>* expected_changed_keys,
     ExtensionSettingsStorage::Result actual) {
-  std::string error;
-
   if (actual.HasError()) {
     return testing::AssertionFailure() <<
         "Expected: " << GetJSON(*expected_settings) <<
         ", " << ToString(*expected_changed_keys) << "\n" <<
         ", actual has error: " << actual.GetError();
   }
-
-  if (!ValuesEqual(expected_settings, actual.GetSettings(), &error)) {
-    return testing::AssertionFailure() << "For settings, " << error;
+  if (expected_settings == NULL && actual.GetSettings() != NULL) {
+    return testing::AssertionFailure() <<
+        "Expected NULL settings, actual: " << GetJSON(*actual.GetSettings());
   }
-
-  if (!expected_changed_keys && actual.GetChangedKeys()) {
+  if (expected_changed_keys == NULL && actual.GetChangedKeys() != NULL) {
     return testing::AssertionFailure() <<
         "Expected NULL changed keys, actual: " <<
         ToString(*actual.GetChangedKeys());
   }
-  if (expected_changed_keys && !actual.GetChangedKeys()) {
+  if (expected_settings != NULL && actual.GetSettings() == NULL) {
+    return testing::AssertionFailure() <<
+        "Expected: " << GetJSON(*expected_settings) << ", actual NULL";
+  }
+  if (expected_changed_keys != NULL && actual.GetChangedKeys() == NULL) {
     return testing::AssertionFailure() <<
         "Expected: " << ToString(*expected_changed_keys) << ", actual NULL";
   }
+  if (expected_settings != actual.GetSettings() &&
+      !expected_settings->Equals(actual.GetSettings())) {
+    return testing::AssertionFailure() <<
+        "Expected: " << GetJSON(*expected_settings) <<
+        ", actual: " << GetJSON(*actual.GetSettings());
+  }
   if (expected_changed_keys != actual.GetChangedKeys() &&
         *expected_changed_keys != *actual.GetChangedKeys()) {
     return testing::AssertionFailure() <<
         "Expected: " << ToString(*expected_changed_keys) <<
         ", actual: " << ToString(*actual.GetChangedKeys());
   }
-
-  const std::set<std::string>* changed_keys = actual.GetChangedKeys();
-  if (changed_keys) {
-    for (std::set<std::string>::const_iterator it = changed_keys->begin();
-        it != changed_keys->end(); ++it) {
-      Value *expected_old_value = NULL;
-      expected_old_settings->GetWithoutPathExpansion(*it, &expected_old_value);
-      if (!ValuesEqual(expected_old_value, actual.GetOldValue(*it), &error)) {
-        return testing::AssertionFailure() << "Old values not equal: " << error;
-      }
-
-      Value *expected_new_value = NULL;
-      if (expected_settings) {
-        expected_settings->GetWithoutPathExpansion(*it, &expected_new_value);
-      }
-      if (!ValuesEqual(expected_new_value, actual.GetNewValue(*it), &error)) {
-        return testing::AssertionFailure() << "New values not equal: " << error;
-      }
-    }
-  }
-
   return testing::AssertionSuccess();
 }
 
@@ -120,11 +82,10 @@ ExtensionSettingsStorageTest::ExtensionSettingsStorageTest()
     : key1_("foo"),
       key2_("bar"),
       key3_("baz"),
-      empty_dict_(new DictionaryValue()),
-      dict1_(new DictionaryValue()),
-      dict3_(new DictionaryValue()),
-      dict12_(new DictionaryValue()),
-      dict123_(new DictionaryValue()),
+      empty_dict_(new DictionaryValue),
+      dict1_(new DictionaryValue),
+      dict12_(new DictionaryValue),
+      dict123_(new DictionaryValue),
       ui_thread_(BrowserThread::UI, MessageLoop::current()),
       file_thread_(BrowserThread::FILE, MessageLoop::current()) {
   val1_.reset(Value::CreateStringValue(key1_ + "Value"));
@@ -150,7 +111,6 @@ ExtensionSettingsStorageTest::ExtensionSettingsStorageTest()
   set123_.insert(list123_.begin(), list123_.end());
 
   dict1_->Set(key1_, val1_->DeepCopy());
-  dict3_->Set(key3_, val3_->DeepCopy());
   dict12_->Set(key1_, val1_->DeepCopy());
   dict12_->Set(key2_, val2_->DeepCopy());
   dict123_->Set(key1_, val1_->DeepCopy());
@@ -171,179 +131,179 @@ void ExtensionSettingsStorageTest::TearDown() {
 }
 
 TEST_P(ExtensionSettingsStorageTest, GetWhenEmpty) {
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(empty_list_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list123_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(empty_list_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get());
 }
 
 TEST_P(ExtensionSettingsStorageTest, GetWithSingleValue) {
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), empty_dict_.get(), &set1_, storage_->Set(key1_, *val1_));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key2_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key3_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(empty_list_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get(list123_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), &set1_, storage_->Set(key1_, *val1_));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key2_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key3_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(empty_list_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get(list123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get());
 }
 
 TEST_P(ExtensionSettingsStorageTest, GetWithMultipleValues) {
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), empty_dict_.get(), &set12_, storage_->Set(*dict12_));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key3_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(empty_list_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), NULL, NULL, storage_->Get(list123_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), &set12_, storage_->Set(*dict12_));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key3_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(empty_list_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), NULL, storage_->Get(list123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), NULL, storage_->Get());
 }
 
 TEST_P(ExtensionSettingsStorageTest, RemoveWhenEmpty) {
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, empty_dict_.get(), &empty_set_, storage_->Remove(key1_));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &empty_set_, storage_->Remove(key1_));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get());
 }
 
 TEST_P(ExtensionSettingsStorageTest, RemoveWithSingleValue) {
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), empty_dict_.get(), &set1_, storage_->Set(*dict1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, dict1_.get(), &set1_, storage_->Remove(key1_));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key2_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list12_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), &set1_, storage_->Set(*dict1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &set1_, storage_->Remove(key1_));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key2_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list12_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get());
 }
 
 TEST_P(ExtensionSettingsStorageTest, RemoveWithMultipleValues) {
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict123_.get(), empty_dict_.get(), &set123_, storage_->Set(*dict123_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, dict3_.get(), &set3_, storage_->Remove(key3_));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key3_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(empty_list_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get(list1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), NULL, NULL, storage_->Get(list12_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get(list13_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), NULL, NULL, storage_->Get(list123_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), NULL, NULL, storage_->Get());
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, dict12_.get(), &set12_, storage_->Remove(list12_));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key3_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(empty_list_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list12_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list13_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list123_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict123_.get(), &set123_, storage_->Set(*dict123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &set3_, storage_->Remove(key3_));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key3_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(empty_list_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get(list1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), NULL, storage_->Get(list12_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get(list13_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), NULL, storage_->Get(list123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), NULL, storage_->Get());
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &set12_, storage_->Remove(list12_));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key3_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(empty_list_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list12_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list13_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get());
 }
 
 TEST_P(ExtensionSettingsStorageTest, SetWhenOverwriting) {
   DictionaryValue key1_val2;
   key1_val2.Set(key1_, val2_->DeepCopy());
 
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &key1_val2, empty_dict_.get(), &set1_, storage_->Set(key1_, *val2_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), &key1_val2, &set12_, storage_->Set(*dict12_));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key3_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(empty_list_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get(list1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), NULL, NULL, storage_->Get(list12_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), NULL, NULL, storage_->Get(list13_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), NULL, NULL, storage_->Get(list123_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &key1_val2, &set1_, storage_->Set(key1_, *val2_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), &set12_, storage_->Set(*dict12_));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key3_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(empty_list_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get(list1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), NULL, storage_->Get(list12_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), NULL, storage_->Get(list13_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), NULL, storage_->Get(list123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), NULL, storage_->Get());
 }
 
 TEST_P(ExtensionSettingsStorageTest, ClearWhenEmpty) {
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, empty_dict_.get(), &empty_set_, storage_->Clear());
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(empty_list_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list123_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &empty_set_, storage_->Clear());
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(empty_list_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get());
 }
 
 TEST_P(ExtensionSettingsStorageTest, ClearWhenNotEmpty) {
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), empty_dict_.get(), &set12_, storage_->Set(*dict12_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, dict12_.get(), &set12_, storage_->Clear());
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(empty_list_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(list123_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), &set12_, storage_->Set(*dict12_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &set12_, storage_->Clear());
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(empty_list_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(list123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get());
 }
 
 // Dots should be allowed in key names; they shouldn't be interpreted as
@@ -358,35 +318,33 @@ TEST_P(ExtensionSettingsStorageTest, DotsInKeyNames) {
   DictionaryValue dot_dict;
   dot_dict.SetWithoutPathExpansion(dot_key, dot_value.DeepCopy());
 
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(dot_key));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &dot_dict, empty_dict_.get(), &dot_set,
-      storage_->Set(dot_key, dot_value));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &dot_dict, &dot_dict, &empty_set_,
-      storage_->Set(dot_key, dot_value));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &dot_dict, NULL, NULL, storage_->Get(dot_key));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, &dot_dict, &dot_set, storage_->Remove(dot_key));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, empty_dict_.get(), &empty_set_, storage_->Remove(dot_key));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &dot_dict, empty_dict_.get(), &dot_set, storage_->Set(dot_dict));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &dot_dict, NULL, NULL, storage_->Get(dot_list));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &dot_dict, NULL, NULL, storage_->Get());
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, &dot_dict, &dot_set, storage_->Remove(dot_list));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get(dot_key));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(dot_key));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &dot_dict, &dot_set, storage_->Set(dot_key, dot_value));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &dot_dict, &empty_set_, storage_->Set(dot_key, dot_value));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &dot_dict, NULL, storage_->Get(dot_key));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &dot_set, storage_->Remove(dot_key));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &empty_set_, storage_->Remove(dot_key));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &dot_dict, &dot_set, storage_->Set(dot_dict));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &dot_dict, NULL, storage_->Get(dot_list));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &dot_dict, NULL, storage_->Get());
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &dot_set, storage_->Remove(dot_list));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get(dot_key));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get());
 }
 
 TEST_P(ExtensionSettingsStorageTest, DotsInKeyNamesWithDicts) {
@@ -397,12 +355,12 @@ TEST_P(ExtensionSettingsStorageTest, DotsInKeyNamesWithDicts) {
   std::set<std::string> changed_keys;
   changed_keys.insert("foo");
 
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &outer_dict, empty_dict_.get(), &changed_keys, storage_->Set(outer_dict));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &outer_dict, NULL, NULL, storage_->Get("foo"));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      empty_dict_.get(), NULL, NULL, storage_->Get("foo.bar"));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &outer_dict, &changed_keys, storage_->Set(outer_dict));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &outer_dict, NULL, storage_->Get("foo"));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      empty_dict_.get(), NULL, storage_->Get("foo.bar"));
 }
 
 TEST_P(ExtensionSettingsStorageTest, ComplexChangedKeysScenarios) {
@@ -413,82 +371,66 @@ TEST_P(ExtensionSettingsStorageTest, ComplexChangedKeysScenarios) {
   std::vector<std::string> complex_list;
   std::set<std::string> complex_set;
   DictionaryValue complex_dict;
-  DictionaryValue complex_changed_dict;
 
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), empty_dict_.get(), &set1_, storage_->Set(key1_, *val1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), dict1_.get(), &empty_set_, storage_->Set(key1_, *val1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), &set1_, storage_->Set(key1_, *val1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), &empty_set_, storage_->Set(key1_, *val1_));
 
   complex_dict.Clear();
   complex_dict.Set(key1_, val2_->DeepCopy());
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &complex_dict, dict1_.get(), &set1_, storage_->Set(key1_, *val2_));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, &complex_dict, &set1_, storage_->Remove(key1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, empty_dict_.get(), &empty_set_, storage_->Remove(key1_));
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict1_.get(), empty_dict_.get(), &set1_, storage_->Set(key1_, *val1_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, dict1_.get(), &set1_, storage_->Clear());
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, empty_dict_.get(), &empty_set_, storage_->Clear());
-
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), empty_dict_.get(), &set12_, storage_->Set(*dict12_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict12_.get(), dict12_.get(), &empty_set_, storage_->Set(*dict12_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      dict123_.get(), dict12_.get(), &set3_, storage_->Set(*dict123_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &complex_dict, &set1_, storage_->Set(key1_, *val2_));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &set1_, storage_->Remove(key1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &empty_set_, storage_->Remove(key1_));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict1_.get(), &set1_, storage_->Set(key1_, *val1_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &set1_, storage_->Clear());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &empty_set_, storage_->Clear());
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), &set12_, storage_->Set(*dict12_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict12_.get(), &empty_set_, storage_->Set(*dict12_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      dict123_.get(), &set3_, storage_->Set(*dict123_));
 
   complex_dict.Clear();
   complex_dict.Set(key1_, val2_->DeepCopy());
   complex_dict.Set(key2_, val2_->DeepCopy());
   complex_dict.Set("asdf", val1_->DeepCopy());
   complex_dict.Set("qwerty", val3_->DeepCopy());
-  complex_changed_dict.Clear();
-  complex_changed_dict.Set(key1_, val1_->DeepCopy());
-  complex_changed_dict.Set(key2_, val2_->DeepCopy());
   complex_set.clear();
   complex_set.insert(key1_);
   complex_set.insert("asdf");
   complex_set.insert("qwerty");
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      &complex_dict, &complex_changed_dict, &complex_set,
-      storage_->Set(complex_dict));
-
-  complex_changed_dict.Clear();
-  complex_changed_dict.Set(key1_, val2_->DeepCopy());
-  complex_changed_dict.Set(key2_, val2_->DeepCopy());
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, &complex_changed_dict, &set12_, storage_->Remove(list12_));
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, empty_dict_.get(), &empty_set_, storage_->Remove(list12_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      &complex_dict, &complex_set, storage_->Set(complex_dict));
+
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &set12_, storage_->Remove(list12_));
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &empty_set_, storage_->Remove(list12_));
 
   complex_list.clear();
   complex_list.push_back(key1_);
   complex_list.push_back("asdf");
-  complex_changed_dict.Clear();
-  complex_changed_dict.Set("asdf", val1_->DeepCopy());
   complex_set.clear();
   complex_set.insert("asdf");
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL,
-      &complex_changed_dict,
-      &complex_set,
-      storage_->Remove(complex_list));
-
-  complex_changed_dict.Clear();
-  complex_changed_dict.Set(key3_, val3_->DeepCopy());
-  complex_changed_dict.Set("qwerty", val3_->DeepCopy());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &complex_set, storage_->Remove(complex_list));
+
   complex_set.clear();
   complex_set.insert(key3_);
   complex_set.insert("qwerty");
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, &complex_changed_dict, &complex_set, storage_->Clear());
-  EXPECT_PRED_FORMAT4(SettingsEq,
-      NULL, empty_dict_.get(), &empty_set_, storage_->Clear());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &complex_set, storage_->Clear());
+  EXPECT_PRED_FORMAT3(SettingsEq,
+      NULL, &empty_set_, storage_->Clear());
 }
diff --git a/chrome/browser/extensions/extension_settings_storage_unittest.h b/chrome/browser/extensions/extension_settings_storage_unittest.h
index b78975e..8f306ed 100644
--- a/chrome/browser/extensions/extension_settings_storage_unittest.h
+++ b/chrome/browser/extensions/extension_settings_storage_unittest.h
@@ -8,15 +8,12 @@
 
 #include "testing/gtest/include/gtest/gtest.h"
 
-#include "base/bind.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "base/scoped_temp_dir.h"
 #include "base/task.h"
 #include "chrome/browser/extensions/extension_settings_backend.h"
-#include "chrome/browser/extensions/extension_settings_frontend.h"
-#include "chrome/test/base/testing_profile.h"
 #include "content/browser/browser_thread.h"
 
 // Parameter type for the value-parameterized tests.
@@ -64,7 +61,6 @@ class ExtensionSettingsStorageTest
 
   scoped_ptr<DictionaryValue> empty_dict_;
   scoped_ptr<DictionaryValue> dict1_;
-  scoped_ptr<DictionaryValue> dict3_;
   scoped_ptr<DictionaryValue> dict12_;
   scoped_ptr<DictionaryValue> dict123_;
 
diff --git a/chrome/browser/extensions/extension_settings_sync_unittest.cc b/chrome/browser/extensions/extension_settings_sync_unittest.cc
index 7073475..f9b34f9 100644
--- a/chrome/browser/extensions/extension_settings_sync_unittest.cc
+++ b/chrome/browser/extensions/extension_settings_sync_unittest.cc
@@ -12,12 +12,10 @@
 #include "base/scoped_temp_dir.h"
 #include "base/task.h"
 #include "chrome/browser/extensions/extension_settings_backend.h"
-#include "chrome/browser/extensions/extension_settings_frontend.h"
 #include "chrome/browser/extensions/extension_settings_storage_cache.h"
 #include "chrome/browser/extensions/extension_settings_sync_util.h"
 #include "chrome/browser/extensions/syncable_extension_settings_storage.h"
 #include "chrome/browser/sync/api/sync_change_processor.h"
-#include "chrome/test/base/testing_profile.h"
 #include "content/browser/browser_thread.h"
 
 // TODO(kalman): Integration tests for sync.
@@ -105,8 +103,7 @@ class MockSyncChangeProcessor : public SyncChangeProcessor {
     if (matching_changes.empty()) {
       ADD_FAILURE() << "No matching changes for " << extension_id << "/" <<
           key << " (out of " << changes_.size() << ")";
-      return ExtensionSettingSyncData(
-          SyncChange::ACTION_INVALID, "", "", new DictionaryValue());
+      return ExtensionSettingSyncData(SyncChange::ACTION_INVALID, "", "", NULL);
     }
     if (matching_changes.size() != 1u) {
       ADD_FAILURE() << matching_changes.size() << " matching changes for " <<
@@ -119,27 +116,25 @@ class MockSyncChangeProcessor : public SyncChangeProcessor {
   ExtensionSettingSyncDataList changes_;
 };
 
-// To be called as a callback from ExtensionSettingsFrontend::RunWithSettings.
-void AssignSettings(
-    ExtensionSettingsBackend** dst, ExtensionSettingsBackend* src) {
-  *dst = src;
-}
-
 }  // namespace
 
 class ExtensionSettingsSyncTest : public testing::Test {
  public:
   ExtensionSettingsSyncTest()
       : ui_thread_(BrowserThread::UI, MessageLoop::current()),
-        file_thread_(BrowserThread::FILE, MessageLoop::current()),
-        frontend_(&profile_),
-        backend_(NULL) {
-  }
+        file_thread_(BrowserThread::FILE, MessageLoop::current()) {}
 
   virtual void SetUp() OVERRIDE {
-    frontend_.RunWithBackend(base::Bind(&AssignSettings, &backend_));
-    MessageLoop::current()->RunAllPending();
-    ASSERT_TRUE(backend_ != NULL);
+    ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
+    // TODO(kalman): Use ExtensionSettingsFrontend here?  It would test more
+    // code paths.
+    backend_.reset(new ExtensionSettingsBackend(temp_dir_.path()));
+  }
+
+  virtual void TearDown() OVERRIDE {
+    // Must do this explicitly here so that it's destroyed before the
+    // message loops are.
+    backend_.reset();
   }
 
  protected:
@@ -151,7 +146,10 @@ class ExtensionSettingsSyncTest : public testing::Test {
         backend_->GetStorage(extension_id));
   }
 
-  // Gets all the sync data from |backend_| as a map from extension id to its
+  MockSyncChangeProcessor sync_;
+  scoped_ptr<ExtensionSettingsBackend> backend_;
+
+  // Gets all the sync data from backend_ as a map from extension id to its
   // sync data.
   std::map<std::string, ExtensionSettingSyncDataList> GetAllSyncData() {
     SyncDataList as_list =
@@ -165,17 +163,13 @@ class ExtensionSettingsSyncTest : public testing::Test {
     return as_map;
   }
 
+ private:
+  ScopedTempDir temp_dir_;
+
   // Need these so that the DCHECKs for running on FILE or UI threads pass.
   MessageLoop message_loop_;
   BrowserThread ui_thread_;
   BrowserThread file_thread_;
-
-  MockSyncChangeProcessor sync_;
-  TestingProfile profile_;
-  ExtensionSettingsFrontend frontend_;
-
-  // Get from frontend_->RunWithBackend, so weak reference.
-  ExtensionSettingsBackend* backend_;
 };
 
 TEST_F(ExtensionSettingsSyncTest, NoDataDoesNotInvokeSync) {
diff --git a/chrome/browser/extensions/in_memory_extension_settings_storage.cc b/chrome/browser/extensions/in_memory_extension_settings_storage.cc
index ee50721..1cb58d5 100644
--- a/chrome/browser/extensions/in_memory_extension_settings_storage.cc
+++ b/chrome/browser/extensions/in_memory_extension_settings_storage.cc
@@ -29,11 +29,11 @@ ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Get(
       settings->SetWithoutPathExpansion(*it, value->DeepCopy());
     }
   }
-  return Result(settings, NULL, NULL);
+  return Result(settings, NULL);
 }
 
 ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Get() {
-  return Result(storage_.DeepCopy(), NULL, NULL);
+  return Result(storage_.DeepCopy(), NULL);
 }
 
 ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Set(
@@ -45,14 +45,11 @@ ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Set(
 
 ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Set(
     const DictionaryValue& settings) {
-  DictionaryValue* old_settings = new DictionaryValue();
   std::set<std::string>* changed_keys = new std::set<std::string>();
   for (DictionaryValue::key_iterator it = settings.begin_keys();
       it != settings.end_keys(); ++it) {
     Value* old_value = NULL;
-    if (storage_.GetWithoutPathExpansion(*it, &old_value)) {
-      old_settings->SetWithoutPathExpansion(*it, old_value->DeepCopy());
-    }
+    storage_.GetWithoutPathExpansion(*it, &old_value);
     Value* new_value = NULL;
     settings.GetWithoutPathExpansion(*it, &new_value);
     if (old_value == NULL || !old_value->Equals(new_value)) {
@@ -60,7 +57,7 @@ ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Set(
       storage_.SetWithoutPathExpansion(*it, new_value->DeepCopy());
     }
   }
-  return Result(settings.DeepCopy(), old_settings, changed_keys);
+  return Result(settings.DeepCopy(), changed_keys);
 }
 
 ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Remove(
@@ -70,17 +67,14 @@ ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Remove(
 
 ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Remove(
     const std::vector<std::string>& keys) {
-  DictionaryValue* old_settings = new DictionaryValue();
   std::set<std::string>* changed_keys = new std::set<std::string>();
   for (std::vector<std::string>::const_iterator it = keys.begin();
       it != keys.end(); ++it) {
-    Value* old_value = NULL;
-    if (storage_.RemoveWithoutPathExpansion(*it, &old_value)) {
-      old_settings->SetWithoutPathExpansion(*it, old_value);
+    if (storage_.RemoveWithoutPathExpansion(*it, NULL)) {
       changed_keys->insert(*it);
     }
   }
-  return Result(NULL, old_settings, changed_keys);
+  return Result(NULL, changed_keys);
 }
 
 ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Clear() {
@@ -89,7 +83,6 @@ ExtensionSettingsStorage::Result InMemoryExtensionSettingsStorage::Clear() {
       it != storage_.end_keys(); ++it) {
     changed_keys->insert(*it);
   }
-  DictionaryValue* old_settings = new DictionaryValue();
-  storage_.Swap(old_settings);
-  return Result(NULL, old_settings, changed_keys);
+  storage_.Clear();
+  return Result(NULL, changed_keys);
 }
diff --git a/chrome/browser/extensions/syncable_extension_settings_storage.cc b/chrome/browser/extensions/syncable_extension_settings_storage.cc
index 8ec5d17..f9820f4 100644
--- a/chrome/browser/extensions/syncable_extension_settings_storage.cc
+++ b/chrome/browser/extensions/syncable_extension_settings_storage.cc
@@ -11,14 +11,8 @@
 #include "content/browser/browser_thread.h"
 
 SyncableExtensionSettingsStorage::SyncableExtensionSettingsStorage(
-    const scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >&
-        observers,
-    const std::string& extension_id,
-    ExtensionSettingsStorage* delegate)
-    : observers_(observers),
-      extension_id_(extension_id),
-      delegate_(delegate),
-      sync_processor_(NULL) {
+    std::string extension_id, ExtensionSettingsStorage* delegate)
+    : extension_id_(extension_id), delegate_(delegate), sync_processor_(NULL) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 }
 
@@ -124,7 +118,7 @@ SyncError SyncableExtensionSettingsStorage::StartSyncing(
         syncable::EXTENSION_SETTINGS);
   }
 
-  const DictionaryValue* settings = maybe_settings.GetSettings();
+  DictionaryValue* settings = maybe_settings.GetSettings();
   if (sync_state.empty()) {
     return SendLocalSettingsToSync(*settings);
   }
@@ -230,88 +224,43 @@ std::vector<SyncError> SyncableExtensionSettingsStorage::ProcessSyncChanges(
   DCHECK(!sync_changes.empty()) << "No sync changes for " << extension_id_;
 
   std::vector<SyncError> errors;
-  ExtensionSettingChanges::Builder changes;
 
   for (ExtensionSettingSyncDataList::const_iterator it = sync_changes.begin();
       it != sync_changes.end(); ++it) {
     DCHECK_EQ(extension_id_, it->extension_id());
-
-    const std::string& key = it->key();
-    const Value& value = it->value();
-
-    scoped_ptr<Value> current_value;
-    {
-      Result maybe_settings = Get(it->key());
-      if (maybe_settings.HasError()) {
-        errors.push_back(SyncError(
-            FROM_HERE,
-            std::string("Error getting current sync state for ") +
-                extension_id_ + "/" + key + ": " + maybe_settings.GetError(),
-            syncable::EXTENSION_SETTINGS));
-        continue;
-      }
-      const DictionaryValue* settings = maybe_settings.GetSettings();
-      if (settings) {
-        Value* value = NULL;
-        if (settings->GetWithoutPathExpansion(key, &value)) {
-          current_value.reset(value->DeepCopy());
-        }
-      }
-    }
-
-    SyncError error;
-
     switch (it->change_type()) {
       case SyncChange::ACTION_ADD:
-        if (!current_value.get()) {
-          error = OnSyncAdd(key, value.DeepCopy(), &changes);
-        } else {
-          // Already a value; hopefully a local change has beaten sync in a
-          // race and it's not a bug, so pretend it's an update.
-          LOG(WARNING) << "Got add from sync for existing setting " <<
-              extension_id_ << "/" << key;
-          error = OnSyncUpdate(
-              key, current_value.release(), value.DeepCopy(), &changes);
-        }
-        break;
-
-      case SyncChange::ACTION_UPDATE:
-        if (current_value.get()) {
-          error = OnSyncUpdate(
-              key, current_value.release(), value.DeepCopy(), &changes);
-        } else {
-          // Similarly, pretend it's an add.
-          LOG(WARNING) << "Got update from sync for nonexistent setting" <<
-              extension_id_ << "/" << key;
-          error = OnSyncAdd(key, value.DeepCopy(), &changes);
+      case SyncChange::ACTION_UPDATE: {
+        synced_keys_.insert(it->key());
+        Result result = delegate_->Set(it->key(), it->value());
+        if (result.HasError()) {
+          errors.push_back(SyncError(
+              FROM_HERE,
+              std::string("Error pushing sync change to local settings: ") +
+                  result.GetError(),
+              syncable::EXTENSION_SETTINGS));
         }
         break;
+      }
 
-      case SyncChange::ACTION_DELETE:
-        if (current_value.get()) {
-          error = OnSyncDelete(key, current_value.release(), &changes);
-        } else {
-          // Similarly, ignore it.
-          LOG(WARNING) << "Got delete from sync for nonexistent setting " <<
-              extension_id_ << "/" << key;
+      case SyncChange::ACTION_DELETE: {
+        synced_keys_.erase(it->key());
+        Result result = delegate_->Remove(it->key());
+        if (result.HasError()) {
+          errors.push_back(SyncError(
+              FROM_HERE,
+              std::string("Error removing sync change from local settings: ") +
+                  result.GetError(),
+              syncable::EXTENSION_SETTINGS));
         }
         break;
+      }
 
       default:
         NOTREACHED();
     }
-
-    if (error.IsSet()) {
-      errors.push_back(error);
-    }
   }
 
-  observers_->Notify(
-      &ExtensionSettingsObserver::OnSettingsChanged,
-      static_cast<Profile*>(NULL),
-      extension_id_,
-      changes.Build());
-
   return errors;
 }
 
@@ -358,18 +307,11 @@ void SyncableExtensionSettingsStorage::SendDeletesToSync(
   SyncChangeList changes;
   for (std::set<std::string>::const_iterator it = keys.begin();
       it != keys.end(); ++it) {
-    if (!synced_keys_.count(*it)) {
-      LOG(WARNING) << "Deleted " << *it << " but no entry in synced_keys";
-      continue;
-    }
+    DCHECK(synced_keys_.count(*it));
     changes.push_back(
         extension_settings_sync_util::CreateDelete(extension_id_, *it));
   }
 
-  if (changes.empty()) {
-    return;
-  }
-
   SyncError error = sync_processor_->ProcessSyncChanges(FROM_HERE, changes);
   if (error.IsSet()) {
     LOG(WARNING) << "Failed to send changes to sync: " << error.message();
@@ -381,58 +323,3 @@ void SyncableExtensionSettingsStorage::SendDeletesToSync(
     synced_keys_.erase(*it);
   }
 }
-
-SyncError SyncableExtensionSettingsStorage::OnSyncAdd(
-    const std::string& key,
-    Value* new_value,
-    ExtensionSettingChanges::Builder* changes) {
-  DCHECK(new_value);
-  synced_keys_.insert(key);
-  Result result = delegate_->Set(key, *new_value);
-  if (result.HasError()) {
-    return SyncError(
-        FROM_HERE,
-        std::string("Error pushing sync add to local settings: ") +
-            result.GetError(),
-        syncable::EXTENSION_SETTINGS);
-  }
-  changes->AppendChange(key, NULL, new_value);
-  return SyncError();
-}
-
-SyncError SyncableExtensionSettingsStorage::OnSyncUpdate(
-    const std::string& key,
-    Value* old_value,
-    Value* new_value,
-    ExtensionSettingChanges::Builder* changes) {
-  DCHECK(old_value);
-  DCHECK(new_value);
-  Result result = delegate_->Set(key, *new_value);
-  if (result.HasError()) {
-    return SyncError(
-        FROM_HERE,
-        std::string("Error pushing sync update to local settings: ") +
-            result.GetError(),
-        syncable::EXTENSION_SETTINGS);
-  }
-  changes->AppendChange(key, old_value, new_value);
-  return SyncError();
-}
-
-SyncError SyncableExtensionSettingsStorage::OnSyncDelete(
-    const std::string& key,
-    Value* old_value,
-    ExtensionSettingChanges::Builder* changes) {
-  DCHECK(old_value);
-  synced_keys_.erase(key);
-  Result result = delegate_->Remove(key);
-  if (result.HasError()) {
-    return SyncError(
-        FROM_HERE,
-        std::string("Error pushing sync remove to local settings: ") +
-            result.GetError(),
-        syncable::EXTENSION_SETTINGS);
-  }
-  changes->AppendChange(key, old_value, NULL);
-  return SyncError();
-}
diff --git a/chrome/browser/extensions/syncable_extension_settings_storage.h b/chrome/browser/extensions/syncable_extension_settings_storage.h
index 499d89c..39f4607 100644
--- a/chrome/browser/extensions/syncable_extension_settings_storage.h
+++ b/chrome/browser/extensions/syncable_extension_settings_storage.h
@@ -8,9 +8,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
-#include "base/observer_list_threadsafe.h"
 #include "base/values.h"
-#include "chrome/browser/extensions/extension_settings_observer.h"
 #include "chrome/browser/extensions/extension_settings_storage.h"
 #include "chrome/browser/extensions/extension_setting_sync_data.h"
 #include "chrome/browser/sync/api/syncable_service.h"
@@ -20,9 +18,7 @@
 class SyncableExtensionSettingsStorage : public ExtensionSettingsStorage {
  public:
   explicit SyncableExtensionSettingsStorage(
-      const scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >&
-          observers,
-      const std::string& extension_id,
+      std::string extension_id,
       // Ownership taken.
       ExtensionSettingsStorage* delegate);
 
@@ -66,26 +62,6 @@ class SyncableExtensionSettingsStorage : public ExtensionSettingsStorage {
   SyncError OverwriteLocalSettingsWithSync(
       const DictionaryValue& sync_state, const DictionaryValue& settings);
 
-  // Called when an Add/Update/Remove comes from sync.  Ownership of Value*s
-  // are taken.
-  SyncError OnSyncAdd(
-      const std::string& key,
-      Value* new_value,
-      ExtensionSettingChanges::Builder* changes);
-  SyncError OnSyncUpdate(
-      const std::string& key,
-      Value* old_value,
-      Value* new_value,
-      ExtensionSettingChanges::Builder* changes);
-  SyncError OnSyncDelete(
-      const std::string& key,
-      Value* old_value,
-      ExtensionSettingChanges::Builder* changes);
-
-  // List of observers to settings changes.
-  const scoped_refptr<ObserverListThreadSafe<ExtensionSettingsObserver> >
-      observers_;
-
   // Id of the extension these settings are for.
   std::string const extension_id_;
 
@@ -96,8 +72,7 @@ class SyncableExtensionSettingsStorage : public ExtensionSettingsStorage {
   // StartSyncing and StopSyncing).
   SyncChangeProcessor* sync_processor_;
 
-  // Keys of the settings that are currently being synced.  Only used to decide
-  // whether an ACTION_ADD or ACTION_UPDATE should be sent to sync on a Set().
+  // Keys of the settings that are currently being synced.
   std::set<std::string> synced_keys_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncableExtensionSettingsStorage);