Add onChanged events to the extension settings API, both from sync and between

chrome/browser/extensions/extension_settings_backend.cc

Index: chrome/browser/extensions/extension_settings_backend.cc
diff --git a/chrome/browser/extensions/extension_settings_backend.cc b/chrome/browser/extensions/extension_settings_backend.cc
index 15963677ff57d13f078996f4be4c54c3e08ad999..796e3c6ba0cbfce7d9fb7e41cf0cad54635f376a 100644
--- a/chrome/browser/extensions/extension_settings_backend.cc
+++ b/chrome/browser/extensions/extension_settings_backend.cc
@@ -36,8 +36,11 @@ const size_t kMaxSettingKeys = 512;
 
 }  // namespace
 
-ExtensionSettingsBackend::ExtensionSettingsBackend(const FilePath& base_path)
+ExtensionSettingsBackend::ExtensionSettingsBackend(
+    const FilePath& base_path,
+    ObserverListThreadSafe<ExtensionSettingsObserver>* observers)
     : base_path_(base_path),
+      observers_(observers),
       sync_processor_(NULL) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 }
@@ -83,7 +86,10 @@ ExtensionSettingsBackend::GetOrCreateStorageWithSyncData(
 
   syncable_storage =
       linked_ptr<SyncableExtensionSettingsStorage>(
-          new SyncableExtensionSettingsStorage(extension_id, storage));
+          new SyncableExtensionSettingsStorage(
+              observers_.get(),
+              extension_id,
+              storage));
   if (sync_processor_) {
     // TODO(kalman): do something if StartSyncing fails.
     ignore_result(syncable_storage->StartSyncing(sync_data, sync_processor_));
@@ -93,6 +99,17 @@ ExtensionSettingsBackend::GetOrCreateStorageWithSyncData(
   return syncable_storage.get();
 }
 
+void ExtensionSettingsBackend::TriggerOnSettingsChanged(
+    Profile* profile,
+    const std::string& extension_id,
+    const std::string& event_json) {
+  observers_->Notify(
+      &ExtensionSettingsObserver::OnSettingsChanged,
+      profile,
+      extension_id,
+      event_json);
+}
+
 std::set<std::string> ExtensionSettingsBackend::GetKnownExtensionIDs() const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   std::set<std::string> result;