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

chrome/browser/ui/views/accelerator_utils_views.cc

Index: chrome/browser/ui/views/accelerator_utils_views.cc
diff --git a/chrome/browser/ui/views/accelerator_utils_views.cc b/chrome/browser/ui/views/accelerator_utils_views.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4520e7cf07eb7c9cd4de9ea835708d3005c9cb67
--- /dev/null
+++ b/chrome/browser/ui/views/accelerator_utils_views.cc
@@ -0,0 +1,23 @@
+// Copyright (c) 2013 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 "ui/base/accelerators/accelerator.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_finder.h"
+#include "chrome/browser/ui/views/frame/browser_view.h"
+
+namespace chrome {
+
+bool IsChromeAccelerator(const ui::Accelerator& accelerator, Profile* profile) {
+  Browser* browser = chrome::FindLastActiveWithProfile(
+      profile, chrome::HOST_DESKTOP_TYPE_NATIVE);
+  if (!browser)
+    return false;
+  BrowserView* browser_view = BrowserView::GetBrowserViewForNativeWindow(
+      browser->window()->GetNativeWindow());
+  return browser_view->IsAcceleratorRegistered(accelerator);
+}
+
+}  // namespace chrome