[Sync] Replace uses of ObserverListThreadSafe with WeakHandles

chrome/browser/sync/js/js_mutation_event_observer.h

 // 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_SYNC_JS_JS_MUTATION_EVENT_OBSERVER_H_
 #define CHROME_BROWSER_SYNC_JS_JS_MUTATION_EVENT_OBSERVER_H_
 #pragma once
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/memory/weak_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "chrome/browser/sync/internal_api/sync_manager.h"
 #include "chrome/browser/sync/syncable/transaction_observer.h"
 #include "chrome/browser/sync/util/weak_handle.h"
 
 namespace tracked_objects {
 class Location;
 }  // namespace tracked_objects
 
 namespace browser_sync {
 
 class JsEventDetails;
 class JsEventHandler;
 
 // Observes all change- and transaction-related events and routes a
 // summarized version to a JsEventHandler.
 class JsMutationEventObserver
     : public sync_api::SyncManager::ChangeObserver,
       public syncable::TransactionObserver {
  public:
   JsMutationEventObserver();
 
   virtual ~JsMutationEventObserver();
 
+  base::WeakPtr<JsMutationEventObserver> AsWeakPtr();
+
+  void InvalidateWeakPtrs();
+
   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;
 
   // syncable::TransactionObserver implementation.
   virtual void OnTransactionStart(
       const tracked_objects::Location& location,
       const syncable::WriterTag& writer) OVERRIDE;
   virtual void OnTransactionWrite(
       const syncable::ImmutableWriteTransactionInfo& write_transaction_info,
       const syncable::ModelTypeBitSet& models_with_changes) OVERRIDE;
   virtual void OnTransactionEnd(
       const tracked_objects::Location& location,
       const syncable::WriterTag& writer) OVERRIDE;
 
  private:
   base::NonThreadSafe non_thread_safe_;
+  base::WeakPtrFactory<JsMutationEventObserver> weak_ptr_factory_;
   WeakHandle<JsEventHandler> event_handler_;
 
   void HandleJsEvent(
     const tracked_objects::Location& from_here,
     const std::string& name, const JsEventDetails& details);
 
   DISALLOW_COPY_AND_ASSIGN(JsMutationEventObserver);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_JS_JS_MUTATION_EVENT_OBSERVER_H_