Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/renderer/manifest/manifest_manager.h

 // Copyright 2014 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_MANIFEST_MANIFEST_MANAGER_H_
 #define CONTENT_RENDERER_MANIFEST_MANIFEST_MANAGER_H_
 
 #include <list>
 #include <memory>
 
@@ skipping 36 matching lines @@
   void DidChangeManifest() override;
   void DidCommitProvisionalLoad(bool is_new_navigation,
                                 bool is_same_page_navigation) override;
 
  private:
   enum ResolveState {
     ResolveStateSuccess,
     ResolveStateFailure
   };
 
+  // RenderFrameObserver implementation.
+  void OnDestruct() override;
+
   // Called when receiving a ManifestManagerMsg_RequestManifest from the browser
   // process.
   void OnHasManifest(int request_id);
   void OnRequestManifest(int request_id);
   void OnRequestManifestComplete(int request_id,
                                  const Manifest&,
                                  const ManifestDebugInfo&);
 
   void FetchManifest();
   void OnManifestFetchComplete(const GURL& document_url,
@@ skipping 19 matching lines @@
   ManifestDebugInfo manifest_debug_info_;
 
   std::list<GetManifestCallback> pending_callbacks_;
 
   DISALLOW_COPY_AND_ASSIGN(ManifestManager);
 };
 
 } // namespace content
 
 #endif  // CONTENT_RENDERER_MANIFEST_MANIFEST_MANAGER_H_