[Sync] Refactor non-frontend DTC to handle new API properly.

chrome/browser/extensions/extension_settings_backend.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_EXTENSIONS_EXTENSION_SETTINGS_BACKEND_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_BACKEND_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "base/task.h"
 #include "chrome/browser/extensions/syncable_extension_settings_storage.h"
 #include "chrome/browser/sync/api/syncable_service.h"
 
 // Manages ExtensionSettingsStorage objects for extensions, including routing
 // changes from sync to them.
 // Lives entirely on the FILE thread.
-class ExtensionSettingsBackend : public SyncableService {
+class ExtensionSettingsBackend
+    : public SyncableService,
+      public base::SupportsWeakPtr<ExtensionSettingsBackend> {
  public:
   // File path is the base of the extension settings directory.
   // The databases will be at base_path/extension_id.
   explicit ExtensionSettingsBackend(const FilePath& base_path);
 
   virtual ~ExtensionSettingsBackend();
 
   // Gets a weak reference to the storage area for a given extension.
   // Must be run on the FILE thread.
   //
@@ skipping 36 matching lines @@
       StorageObjMap;
   mutable StorageObjMap storage_objs_;
 
   // Current sync processor, if any.
   SyncChangeProcessor* sync_processor_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionSettingsBackend);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_BACKEND_H_