android: Fix ContentViewCore and RenderWidgetHostViewAndroid lifetime issue

content/browser/android/content_view_core_impl.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 CONTENT_BROWSER_ANDROID_CONTENT_VIEW_CORE_IMPL_H_
 #define CONTENT_BROWSER_ANDROID_CONTENT_VIEW_CORE_IMPL_H_
 
 #include <vector>
 
 #include "base/android/jni_android.h"
@@ skipping 315 matching lines @@
   friend class ContentViewUserData;
   virtual ~ContentViewCoreImpl();
 
   // NotificationObserver implementation.
   virtual void Observe(int type,
                        const NotificationSource& source,
                        const NotificationDetails& details) OVERRIDE;
 
   // WebContentsObserver implementation.
   virtual void RenderViewReady() OVERRIDE;
+  virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE;
 
   // --------------------------------------------------------------------------
   // Other private methods and data
   // --------------------------------------------------------------------------
 
   void InitWebContents();
 
   RenderWidgetHostViewAndroid* GetRenderWidgetHostViewAndroid();
 
   float GetTouchPaddingDip();
@@ skipping 49 matching lines @@
   bool geolocation_needs_pause_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentViewCoreImpl);
 };
 
 bool RegisterContentViewCore(JNIEnv* env);
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_ANDROID_CONTENT_VIEW_CORE_IMPL_H_