Add histograms to track synced pref changes.

chrome/browser/prefs/pref_service_syncable.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/prefs/pref_service_syncable.h"
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/prefs/default_pref_store.h"
 #include "base/prefs/overlay_user_pref_store.h"
@@ skipping 129 matching lines @@
 }
 
 void PrefServiceSyncable::UpdateCommandLinePrefStore(
     PrefStore* cmd_line_store) {
   // If |pref_service_forked_| is true, then this PrefService and the forked
   // copies will be out of sync.
   DCHECK(!pref_service_forked_);
   PrefService::UpdateCommandLinePrefStore(cmd_line_store);
 }
 
+void PrefServiceSyncable::AddSyncedPrefObserver(const std::string& name,
+    SyncedPrefObserver* observer) {

[battre, 2013/08/06 15:54:39]

nit: align parameters, also below

[Ken Rockot(use gerrit already), 2013/08/06 20:18:32]

Done.

+  pref_sync_associator_.AddSyncedPrefObserver(name, observer);
+  priority_pref_sync_associator_.AddSyncedPrefObserver(name, observer);
+}
+
+void PrefServiceSyncable::RemoveSyncedPrefObserver(const std::string& name,
+    SyncedPrefObserver* observer) {
+  pref_sync_associator_.RemoveSyncedPrefObserver(name, observer);
+  priority_pref_sync_associator_.RemoveSyncedPrefObserver(name, observer);
+}
+
 void PrefServiceSyncable::AddRegisteredSyncablePreference(
     const char* path,
     const user_prefs::PrefRegistrySyncable::PrefSyncStatus sync_status) {
   DCHECK(FindPreference(path));
   if (sync_status == user_prefs::PrefRegistrySyncable::SYNCABLE_PREF) {
     pref_sync_associator_.RegisterPref(path);
   } else if (sync_status ==
              user_prefs::PrefRegistrySyncable::SYNCABLE_PRIORITY_PREF) {
     priority_pref_sync_associator_.RegisterPref(path);
   } else {
     NOTREACHED() << "invalid sync_status: " << sync_status;
   }
 }
 
 void PrefServiceSyncable::OnIsSyncingChanged() {
   FOR_EACH_OBSERVER(PrefServiceSyncableObserver, observer_list_,
                     OnIsSyncingChanged());
 }
 
 void PrefServiceSyncable::ProcessPrefChange(const std::string& name) {
   pref_sync_associator_.ProcessPrefChange(name);
   priority_pref_sync_associator_.ProcessPrefChange(name);
 }