Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/renderer/screen_orientation/screen_orientation_dispatcher.h

 // Copyright 2014 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_SCREEN_ORIENTATION_SCREEN_ORIENTATION_DISPATCHER_H_
 #define CONTENT_RENDERER_SCREEN_ORIENTATION_SCREEN_ORIENTATION_DISPATCHER_H_
 
 #include "base/compiler_specific.h"
 #include "base/id_map.h"
 #include "base/macros.h"
@@ skipping 16 matching lines @@
     NON_EXPORTED_BASE(public blink::WebScreenOrientationClient) {
  public:
   explicit ScreenOrientationDispatcher(RenderFrame* render_frame);
   ~ScreenOrientationDispatcher() override;
 
  private:
   friend class ScreenOrientationDispatcherTest;
 
   // RenderFrameObserver implementation.
   bool OnMessageReceived(const IPC::Message& message) override;
+  void OnDestruct() override;
 
   // blink::WebScreenOrientationClient implementation.
   void lockOrientation(blink::WebScreenOrientationLockType orientation,
                        blink::WebLockOrientationCallback* callback) override;
   void unlockOrientation() override;
 
   void OnLockSuccess(int request_id);
   void OnLockError(int request_id,
                    blink::WebLockOrientationError error);
 
   void CancelPendingLocks();
 
   // The pending_callbacks_ map is mostly meant to have a unique ID to associate
   // with every callback going trough the dispatcher. The map will own the
   // pointer in the sense that it will destroy it when Remove() will be called.
   // Furthermore, we only expect to have one callback at a time in this map,
   // which is what IDMap was designed for.
   typedef IDMap<blink::WebLockOrientationCallback, IDMapOwnPointer> CallbackMap;
   CallbackMap pending_callbacks_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenOrientationDispatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_SCREEN_ORIENTATION_SCREEN_ORIENTATION_DISPATCHER_H_