Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

extensions/renderer/extension_frame_helper.h

 // Copyright 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 EXTENSIONS_RENDERER_EXTENSION_FRAME_HELPER_H_
 #define EXTENSIONS_RENDERER_EXTENSION_FRAME_HELPER_H_
 
 #include <vector>
 
 #include "base/macros.h"
@@ skipping 75 matching lines @@
   void DidCreateNewDocument() override;
   void DidMatchCSS(
       const blink::WebVector<blink::WebString>& newly_matching_selectors,
       const blink::WebVector<blink::WebString>& stopped_matching_selectors)
           override;
   void DidCreateScriptContext(v8::Local<v8::Context>,
                               int extension_group,
                               int world_id) override;
   void WillReleaseScriptContext(v8::Local<v8::Context>, int world_id) override;
   bool OnMessageReceived(const IPC::Message& message) override;
+  void OnDestruct() override;
 
   // IPC handlers.
   void OnExtensionValidateMessagePort(int port_id);
   void OnExtensionDispatchOnConnect(
       int target_port_id,
       const std::string& channel_name,
       const ExtensionMsg_TabConnectionInfo& source,
       const ExtensionMsg_ExternalConnectionInfo& info,
       const std::string& tls_channel_id);
   void OnExtensionDeliverMessage(int target_port_id,
@@ skipping 35 matching lines @@
   std::vector<base::Closure> document_load_finished_callbacks_;
 
   base::WeakPtrFactory<ExtensionFrameHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionFrameHelper);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_EXTENSION_FRAME_HELPER_H_