Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/renderer/devtools/devtools_agent.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_DEVTOOLS_DEVTOOLS_AGENT_H_
 #define CONTENT_RENDERER_DEVTOOLS_DEVTOOLS_AGENT_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 38 matching lines @@
   blink::WebDevToolsAgent* GetWebAgent();
 
   bool IsAttached();
 
  private:
   friend class DevToolsAgentTest;
 
   // RenderFrameObserver implementation.
   bool OnMessageReceived(const IPC::Message& message) override;
   void WidgetWillClose() override;
+  void OnDestruct() override;
 
   // WebDevToolsAgentClient implementation.
   void sendProtocolMessage(int session_id,
                            int call_id,
                            const blink::WebString& response,
                            const blink::WebString& state) override;
   blink::WebDevToolsAgentClient::WebKitClientMessageLoop*
       createClientMessageLoop() override;
   void willEnterDebugLoop() override;
   void didExitDebugLoop() override;
@@ skipping 33 matching lines @@
       send_protocol_message_callback_for_test_;
   std::unique_ptr<DevToolsCPUThrottler> cpu_throttler_;
   base::WeakPtrFactory<DevToolsAgent> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DevToolsAgent);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_DEVTOOLS_DEVTOOLS_AGENT_H_