Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/renderer/render_view_mouse_lock_dispatcher.h

 // Copyright (c) 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 CONTENT_RENDERER_RENDER_VIEW_MOUSE_LOCK_DISPATCHER_H_
 #define CONTENT_RENDERER_RENDER_VIEW_MOUSE_LOCK_DISPATCHER_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/public/renderer/render_view_observer.h"
 #include "content/renderer/mouse_lock_dispatcher.h"
 
 namespace content {
 class RenderViewImpl;
 
 // RenderViewMouseLockDispatcher is owned by RenderViewImpl.
 class RenderViewMouseLockDispatcher : public MouseLockDispatcher,
                                       public RenderViewObserver {
  public:
   explicit RenderViewMouseLockDispatcher(RenderViewImpl* render_view_impl);
   ~RenderViewMouseLockDispatcher() override;
 
  private:
   // MouseLockDispatcher implementation.
   void SendLockMouseRequest(bool unlocked_by_target) override;
   void SendUnlockMouseRequest() override;
 
-  // RenderView::Observer implementation.
+  // RenderViewObserver implementation.
   bool OnMessageReceived(const IPC::Message& message) override;
+  void OnDestruct() override;
 
   void OnLockMouseACK(bool succeeded);
 
   RenderViewImpl* render_view_impl_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderViewMouseLockDispatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_VIEW_MOUSE_LOCK_DISPATCHER_H_