Add CommandDispatcher to BrowserViewController.

ios/chrome/browser/ui/commands/UIKit+ChromeExecuteCommand.h

 // Copyright 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 IOS_CHROME_BROWSER_UI_COMMANDS_UIKIT_CHROMEEXECUTECOMMAND_H_
 #define IOS_CHROME_BROWSER_UI_COMMANDS_UIKIT_CHROMEEXECUTECOMMAND_H_
 
 #import <UIKit/UIKit.h>
 
 @interface UIResponder (ChromeExecuteCommand)
 // Executes a Chrome command.  |sender| must implement the |-tag| method and
 // return the id of the command to execute.  The default implementation of this
 // method simply forwards the call to the next responder.
 - (IBAction)chromeExecuteCommand:(id)sender;
 @end
 
 @interface UIWindow (ChromeExecuteCommand)
 // UIResponder addition to execute a Chrome command.  Overridden in UIWindow to
 // forward the call to the application's delegate.
 - (void)chromeExecuteCommand:(id)sender;
 @end
 
+@protocol ChromeExecuteCommand
+// Executes a Chrome command.  |sender| must implement the |-tag| method and
+// return the id of the command to execute.  The default implementation of this
+// method simply forwards the call to the next responder.
+- (IBAction)chromeExecuteCommand:(id)sender;
+@end
+
 #endif  // IOS_CHROME_BROWSER_UI_COMMANDS_UIKIT_CHROMEEXECUTECOMMAND_H_