Move command handling and updating off Browser and onto a helper object.

chrome/browser/command_observer.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_COMMAND_OBSERVER_H_
+#define CHROME_BROWSER_COMMAND_OBSERVER_H_
+#pragma once
+
+// An Observer interface implemented by objects that want to be informed when
+// the state of a particular command ID is modified. See CommandUpdater.
+class CommandObserver {
+ public:
+  // Notifies the observer that the enabled state has changed for the
+  // specified command id.
+  virtual void EnabledStateChangedForCommand(int id, bool enabled) = 0;
+
+ protected:
+  virtual ~CommandObserver();
+};
+
+#endif  // CHROME_BROWSER_COMMAND_OBSERVER_H_