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

chrome/browser/ui/views/frame/browser_view.h

Index: chrome/browser/ui/views/frame/browser_view.h
diff --git a/chrome/browser/ui/views/frame/browser_view.h b/chrome/browser/ui/views/frame/browser_view.h
index 813acb3a996d106b9b0e809051bff6c5bc3e25be..9f9f66f72795f1f57432bb87c99d06b275de057f 100644
--- a/chrome/browser/ui/views/frame/browser_view.h
+++ b/chrome/browser/ui/views/frame/browser_view.h
@@ -188,6 +188,9 @@ class BrowserView : public BrowserWindow,
   // otherwise.
   bool GetAccelerator(int cmd_id, ui::Accelerator* accelerator);
 
+  // Returns true if the specificed |accelerator| is registered with this view.
+  bool IsAcceleratorRegistered(const ui::Accelerator& accelerator);
+
   // Returns the active WebContents. Used by our NonClientView's
   // TabIconView::TabContentsProvider implementations.
   // TODO(beng): exposing this here is a bit bogus, since it's only used to