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

chrome/browser/extensions/extension_keybinding_registry.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_KEYBINDING_REGISTRY_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_KEYBINDING_REGISTRY_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/notification_source.h"
 
 class Profile;
 
+namespace ui {
+class Accelerator;
+}
+
 namespace extensions {
 
 class ActiveTabPermissionGranter;
 class Extension;
 
 // The ExtensionKeybindingRegistry is a class that handles the cross-platform
 // logic for keyboard accelerators. See platform-specific implementations for
 // implementation details for each platform.
 class ExtensionKeybindingRegistry : public content::NotificationObserver {
  public:
@@ skipping 14 matching lines @@
   ExtensionKeybindingRegistry(Profile* profile,
                               ExtensionFilter extension_filter,
                               Delegate* delegate);
 
   virtual ~ExtensionKeybindingRegistry();
 
   // Enables/Disables general shortcut handing in Chrome. Implemented in
   // platform-specific ExtensionKeybindingsRegistry* files.
   static void SetShortcutHandlingSuspended(bool suspended);
 
+  // Returns true if the given |accelerator| is currently registered by
+  // Chrome. Implemented in platform-specific ExtensionKeybindingsRegistry*
+  // files.
+  static bool IsChromeAccelerator(const ui::Accelerator& accelerator);
+
   // Overridden from content::NotificationObserver:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
  protected:
   // Add extension keybinding for the events defined by the |extension|.
   // |command_name| is optional, but if not blank then only the command
   // specified will be added.
   virtual void AddExtensionKeybinding(
@@ skipping 31 matching lines @@
 
   // Weak pointer to our delegate. Not owned by us. Must outlive this class.
   Delegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionKeybindingRegistry);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_KEYBINDING_REGISTRY_H_