Make sure manifest specified shortcut for Extension Command can not override the built-in shortcuts.

chrome/browser/ui/gtk/extensions/extension_keybinding_registry_gtk.cc

 // Copyright (c) 2012 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/ui/gtk/extensions/extension_keybinding_registry_gtk.h"
 
 #include <gtk/gtk.h>
 
 #include "chrome/browser/extensions/api/commands/command_service.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/ui/gtk/accelerators_gtk.h"
 #include "chrome/common/extensions/extension.h"
 #include "ui/base/accelerators/platform_accelerator_gtk.h"
 
 // static
 void extensions::ExtensionKeybindingRegistry::SetShortcutHandlingSuspended(
     bool suspended) {
   ExtensionKeybindingRegistryGtk::set_shortcut_handling_suspended(suspended);
 }
 
+// static
+bool extensions::ExtensionKeybindingRegistry::IsChromeAccelerator(
+    const ui::Accelerator& accelerator) {
+  AcceleratorsGtk* accelerators = AcceleratorsGtk::GetInstance();
+  for (AcceleratorsGtk::const_iterator iter = accelerators->begin();
+       iter != accelerators->end(); ++iter) {
+    if (iter->second.key_code() == accelerator.key_code() &&
+        iter->second.modifiers() == accelerator.modifiers())
+      return true;
+  }
+  return false;
+}
+
 bool ExtensionKeybindingRegistryGtk::shortcut_handling_suspended_ = false;
 
 ExtensionKeybindingRegistryGtk::ExtensionKeybindingRegistryGtk(
     Profile* profile,
     gfx::NativeWindow window,
     ExtensionFilter extension_filter,
     Delegate* delegate)
     : ExtensionKeybindingRegistry(profile, extension_filter, delegate),
       profile_(profile),
       window_(window),
@@ skipping 131 matching lines @@
 
   EventTargets::iterator it = event_targets_.find(accelerator);
   if (it == event_targets_.end()) {
     NOTREACHED();  // Shouldn't get this event for something not registered.
     return FALSE;
   }
 
   CommandExecuted(it->second.first, it->second.second);
   return TRUE;
 }