Remove Downcasting RVContextMenuBase in ContextMenuDeleagate implementations.

chrome/browser/renderer_context_menu/render_view_context_menu_test_util.cc

 // 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.
 
 #include "chrome/browser/renderer_context_menu/render_view_context_menu_test_util.h"
 #include "content/public/browser/web_contents.h"
 #include "ui/base/models/menu_model.h"
 
 using ui::MenuModel;
 
@@ skipping 47 matching lines @@
         *found_index = i;
         return true;
       } else if (model->GetTypeAt(i) == MenuModel::TYPE_SUBMENU) {
         models_to_search.push_back(model->GetSubmenuModelAt(i));
       }
     }
   }
 
   return false;
 }
+
+void TestRenderViewContextMenu::Show() {
+}