Add OVERRIDEs to RenderViewHostObserver subclasses that didn't already have them.

chrome/browser/renderer_host/render_widget_host_view_mac.mm

 // 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.
 
 #include <QuartzCore/QuartzCore.h>
 
 #include "chrome/browser/renderer_host/render_widget_host_view_mac.h"
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
@@ skipping 183 matching lines @@
 class SpellCheckRenderViewObserver : public RenderViewHostObserver {
  public:
   SpellCheckRenderViewObserver(RenderViewHost* host,
                                RenderWidgetHostViewMac* view)
     : RenderViewHostObserver(host),
       view_(view) {
   }
 
  private:
   // RenderViewHostObserver implementation.
-  virtual bool OnMessageReceived(const IPC::Message& message) {
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE {
     bool handled = true;
     IPC_BEGIN_MESSAGE_MAP(SpellCheckRenderViewObserver, message)
       IPC_MESSAGE_HANDLER(SpellCheckHostMsg_ToggleSpellCheck,
                           OnToggleSpellCheck)
       IPC_MESSAGE_UNHANDLED(handled = false)
     IPC_END_MESSAGE_MAP()
     return handled;
   }
 
   void OnToggleSpellCheck(bool enabled, bool checked) {
@@ skipping 2541 matching lines @@
   if (!string) return NO;
 
   // If the user is currently using an IME, confirm the IME input,
   // and then insert the text from the service, the same as TextEdit and Safari.
   [self confirmComposition];
   [self insertText:string];
   return YES;
 }
 
 @end