components: Cleanup class/struct fwd declarations

components/sync/js/js_controller.h

 // Copyright 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.
 
 #ifndef COMPONENTS_SYNC_JS_JS_CONTROLLER_H_
 #define COMPONENTS_SYNC_JS_JS_CONTROLLER_H_
 
 // See README.js for design comments.
 
 #include <string>
 
 namespace syncer {
 
 class JsEventHandler;
-template <typename T>
-class WeakHandle;
 
 // An interface for objects that JsEventHandlers directly interact
 // with.  JsEventHandlers can add themselves to receive events and
 // also send messages which will eventually reach the backend.
 class JsController {
  public:
   // Adds an event handler which will start receiving JS events (not
   // immediately, so this can be called in the handler's constructor).
   // Multiple event handlers are supported, but each event handler
   // must be added at most once.
   //
   // Ideally, we'd take WeakPtrs, but we need the raw pointer values
   // to be able to look them up for removal.
   virtual void AddJsEventHandler(JsEventHandler* event_handler) = 0;
 
   // Removes the given event handler if it has been added.  It will
   // immediately stop receiving any JS events.
   virtual void RemoveJsEventHandler(JsEventHandler* event_handler) = 0;
 
  protected:
   virtual ~JsController() {}
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_JS_JS_CONTROLLER_H_