Only allow to lock the mouse when the tab is in fullscreen mode.

content/browser/renderer_host/render_view_host_delegate.cc

 // 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 "content/browser/renderer_host/render_view_host_delegate.h"
 
 #include "base/memory/singleton.h"
 #include "content/common/renderer_preferences.h"
 #include "googleurl/src/gurl.h"
 #include "ui/gfx/rect.h"
@@ skipping 25 matching lines @@
 }
 
 WebPreferences RenderViewHostDelegate::GetWebkitPrefs() {
   return WebPreferences();
 }
 
 bool RenderViewHostDelegate::PreHandleKeyboardEvent(
     const NativeWebKeyboardEvent& event, bool* is_keyboard_shortcut) {
   return false;
 }
+
+bool RenderViewHostDelegate::IsFullscreenForCurrentTab() const {
+  return false;
+}