Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

components/translate/content/renderer/translate_helper.h

 // Copyright (c) 2011 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 COMPONENTS_TRANSLATE_CONTENT_RENDERER_TRANSLATE_HELPER_H_
 #define COMPONENTS_TRANSLATE_CONTENT_RENDERER_TRANSLATE_HELPER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 145 matching lines @@
     DEFERRED,  // Language detection couldn't be performed when it was requested
     RESUMED,   // A deferred language detection attempt was completed later
     LANGUAGE_DETECTION_TIMING_MAX_VALUE  // The bounding value for this enum
   };
 
   // Converts language code to the one used in server supporting list.
   static void ConvertLanguageCodeSynonym(std::string* code);
 
   // RenderFrameObserver implementation.
   bool OnMessageReceived(const IPC::Message& message) override;
+  void OnDestruct() override;
 
   // Informs us that the page's text has been extracted.
   void PageCapturedImpl(int page_seq_no, const base::string16& contents);
 
   // Cancels any translation that is currently being performed.  This does not
   // revert existing translations.
   void CancelPendingTranslation();
 
   // Checks if the current running page translation is finished or errored and
   // notifies the browser accordingly.  If the translation has not terminated,
@@ skipping 73 matching lines @@
 
   // Method factory used to make calls to TranslatePageImpl.
   base::WeakPtrFactory<TranslateHelper> weak_method_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TranslateHelper);
 };
 
 }  // namespace translate
 
 #endif  // COMPONENTS_TRANSLATE_CONTENT_RENDERER_TRANSLATE_HELPER_H_