Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/renderer/text_input_client_observer.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_TEXT_INPUT_CLIENT_OBSERVER_H_
 #define CONTENT_RENDERER_TEXT_INPUT_CLIENT_OBSERVER_H_
 
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "content/public/renderer/render_view_observer.h"
@@ skipping 13 matching lines @@
 // content/browser/renderer_host/text_input_client_mac.h for more information.
 class TextInputClientObserver : public RenderViewObserver {
  public:
   explicit TextInputClientObserver(RenderViewImpl* render_view);
   ~TextInputClientObserver() override;
 
   // RenderViewObserver overrides:
   bool OnMessageReceived(const IPC::Message& message) override;
 
  private:
+  // RenderViewObserver implementation.
+  void OnDestruct() override;
+
   // Returns the WebView of the RenderView.
   blink::WebView* webview();
 
   // IPC Message handlers:
   void OnStringAtPoint(gfx::Point point);
   void OnCharacterIndexForPoint(gfx::Point point);
   void OnFirstRectForCharacterRange(gfx::Range range);
   void OnStringForRange(gfx::Range range);
 
 #if defined(ENABLE_PLUGINS)
   RenderViewImpl* const render_view_impl_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(TextInputClientObserver);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_TEXT_INPUT_CLIENT_OBSERVER_H_