Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

chrome/renderer/net/net_error_helper.h

 // Copyright (c) 2013 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_RENDERER_NET_NET_ERROR_HELPER_H_
 #define CHROME_RENDERER_NET_NET_ERROR_HELPER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 43 matching lines @@
   void TrackClick(int tracking_id) override;
 
   // RenderFrameObserver implementation.
   void DidStartProvisionalLoad() override;
   void DidCommitProvisionalLoad(bool is_new_navigation,
                                 bool is_same_page_navigation) override;
   void DidFinishLoad() override;
   void OnStop() override;
   void WasShown() override;
   void WasHidden() override;
+  void OnDestruct() override;
 
   // IPC::Listener implementation.
   bool OnMessageReceived(const IPC::Message& message) override;
 
   // RenderThreadObserver implementation.
   void NetworkStateChanged(bool online) override;
 
   // Initializes |error_html| with the HTML of an error page in response to
   // |error|.  Updates internals state with the assumption the page will be
   // loaded immediately.
@@ skipping 65 matching lines @@
   // Weak factory for vending a weak pointer to a NetErrorPageController. Weak
   // pointers are invalidated on each commit, to prevent getting messages from
   // Controllers used for the previous commit that haven't yet been cleaned up.
   base::WeakPtrFactory<NetErrorPageController::Delegate>
       weak_controller_delegate_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(NetErrorHelper);
 };
 
 #endif  // CHROME_RENDERER_NET_NET_ERROR_HELPER_H_