Remove content::NotificationObserver dependency from most Prefs code.

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

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

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


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

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

2 files changed, 10 insertions, 23 deletions

diff --git a/chrome/browser/chromeos/audio/audio_handler.cc b/chrome/browser/chromeos/audio/audio_handler.cc
index f9d9999..f78657f 100644
--- a/chrome/browser/chromeos/audio/audio_handler.cc
+++ b/chrome/browser/chromeos/audio/audio_handler.cc
@@ -19,7 +19,6 @@
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
-#include "content/public/browser/notification_service.h"
 
 using std::max;
 using std::min;
@@ -161,18 +160,11 @@ void AudioHandler::RemoveVolumeObserver(VolumeObserver* observer) {
   volume_observers_.RemoveObserver(observer);
 }
 
-void AudioHandler::Observe(int type,
-                           const content::NotificationSource& source,
-                           const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* pref_name = content::Details<std::string>(details).ptr();
-    if (*pref_name == prefs::kAudioOutputAllowed ||
-        *pref_name == prefs::kAudioCaptureAllowed) {
-      ApplyAudioPolicy();
-    }
-  } else {
-    NOTREACHED() << "Unexpected notification type : " << type;
-  }
+void AudioHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                       const std::string& pref_name) {
+  DCHECK(pref_name == prefs::kAudioOutputAllowed ||
+         pref_name == prefs::kAudioCaptureAllowed);
+  ApplyAudioPolicy();
 }
 
 AudioHandler::AudioHandler(AudioMixer* mixer)
diff --git a/chrome/browser/chromeos/audio/audio_handler.h b/chrome/browser/chromeos/audio/audio_handler.h
index ecb9f57a..1b77f9f 100644
--- a/chrome/browser/chromeos/audio/audio_handler.h
+++ b/chrome/browser/chromeos/audio/audio_handler.h
@@ -9,11 +9,8 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/threading/thread.h"
-#include "content/public/browser/notification_details.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
-#include "content/public/browser/notification_source.h"
 
 template <typename T> struct DefaultSingletonTraits;
 
@@ -24,7 +21,7 @@ namespace chromeos {
 
 class AudioMixer;
 
-class AudioHandler : public content::NotificationObserver {
+class AudioHandler : public PrefObserver {
  public:
   class VolumeObserver {
    public:
@@ -76,10 +73,9 @@ class AudioHandler : public content::NotificationObserver {
   void AddVolumeObserver(VolumeObserver* observer);
   void RemoveVolumeObserver(VolumeObserver* observer);
 
-  // Overridden from content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   // Defines the delete on exit Singleton traits we like.  Best to have this
@@ -107,7 +103,6 @@ class AudioHandler : public content::NotificationObserver {
   PrefService* local_state_;  // not owned
 
   PrefChangeRegistrar pref_change_registrar_;
-  content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioHandler);
 };