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

chrome/browser/ui/cocoa/extensions/extension_keybinding_registry_cocoa.mm

 // 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/cocoa/extensions/extension_keybinding_registry_cocoa.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/common/extensions/extension.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/extensions/extension_manifest_constants.h"
 #include "content/public/browser/native_web_keyboard_event.h"
 #include "content/public/browser/notification_service.h"
 
 namespace values = extension_manifest_values;
 
 // static
 void extensions::ExtensionKeybindingRegistry::SetShortcutHandlingSuspended(
     bool suspended) {
   ExtensionKeybindingRegistryCocoa::set_shortcut_handling_suspended(suspended);
 }
 
+// static
+bool extensions::ExtensionKeybindingRegistry::IsChromeAccelerator(
+    const ui::Accelerator& accelerator) {
+  // TODO(finnur): Implement this.

[Yoyo Zhou, 2013/04/05 18:09:50]

Is the issue that AcceleratorsCocoa doesn't give you the list of accelerators?

[Finnur, 2013/04/05 19:50:03]

The issue is that the CL for Views and GTK was ready but my Mac tree was ancient
and needed an update and fix for bitrot (an outstanding CL that is on hold but I
don't want to throw away).

But I'm (honestly) very interested in what you are about to tell me. Pretend the
answer is yes. :)

+  return false;
+}
+
 bool ExtensionKeybindingRegistryCocoa::shortcut_handling_suspended_ = false;
 
 ExtensionKeybindingRegistryCocoa::ExtensionKeybindingRegistryCocoa(
     Profile* profile,
     gfx::NativeWindow window,
     ExtensionFilter extension_filter,
     Delegate* delegate)
     : ExtensionKeybindingRegistry(profile, extension_filter, delegate),
       profile_(profile),
       window_(window) {
@@ skipping 105 matching lines @@
     const extensions::Extension* extension,
     const std::string& command_name) {
   EventTargets::iterator iter = event_targets_.begin();
   while (iter != event_targets_.end()) {
     EventTargets::iterator old = iter++;
     if (old->second.first == extension->id() &&
         (command_name.empty() || (old->second.second == command_name)))
       event_targets_.erase(old);
   }
 }