[Sync] Move some code into new class JsMutationEventObserver

chrome/browser/sync/js/js_sync_manager_observer.h

Index: chrome/browser/sync/js/js_sync_manager_observer.h
diff --git a/chrome/browser/sync/js/js_sync_manager_observer.h b/chrome/browser/sync/js/js_sync_manager_observer.h
index d48e8f274a30434e0f4c85f219b2f1910773ff88..0fa1db317e302e5b8b08686c34ba0974a10659c2 100644
--- a/chrome/browser/sync/js/js_sync_manager_observer.h
+++ b/chrome/browser/sync/js/js_sync_manager_observer.h
@@ -24,22 +24,13 @@ class JsEventDetails;
 class JsEventHandler;
 
 // Routes SyncManager events to a JsEventHandler.
-class JsSyncManagerObserver
-    : public sync_api::SyncManager::ChangeObserver,
-      public sync_api::SyncManager::Observer {
+class JsSyncManagerObserver : public sync_api::SyncManager::Observer {
  public:
   JsSyncManagerObserver();
   virtual ~JsSyncManagerObserver();
 
   void SetJsEventHandler(const WeakHandle<JsEventHandler>& event_handler);
 
-  // sync_api::SyncManager::ChangeObserver implementation.
-  virtual void OnChangesApplied(
-      syncable::ModelType model_type,
-      int64 write_transaction_id,
-      const sync_api::ImmutableChangeRecordList& changes) OVERRIDE;
-  virtual void OnChangesComplete(syncable::ModelType model_type) OVERRIDE;
-
   // sync_api::SyncManager::Observer implementation.
   virtual void OnSyncCycleCompleted(
       const sessions::SyncSessionSnapshot* snapshot) OVERRIDE;