Implement first part of supporting global extension commands.

chrome/browser/extensions/global_shortcut_listener.h

+// 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.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_GLOBAL_SHORTCUT_LISTENER_H_
+#define CHROME_BROWSER_EXTENSIONS_GLOBAL_SHORTCUT_LISTENER_H_
+
+#include <map>
+
+#include "base/observer_list.h"
+#include "ui/events/keycodes/keyboard_codes.h"
+#include "ui/gfx/native_widget_types.h"
+
+namespace ui {
+class Accelerator;
+}
+
+namespace extensions {
+
+// Platform-neutral implementation of a class that keeps track of observers and
+// monitors keystrokes. It relays messages to the appropriate observers when a
+// global shortcut has been struck by the user.
+class GlobalShortcutListener {
+ public:
+  class Observer {
+   public:
+    // Called when your global shortcut (|accelerator|) is struck.
+    virtual void OnKeyPressed(const ui::Accelerator& accelerator) = 0;
+  };
+
+  virtual ~GlobalShortcutListener();
+
+  static GlobalShortcutListener* GetInstance();
+
+  // Implemented by platform-specific implementations of this class.
+  virtual void StartListening() = 0;
+  virtual void StopListening() = 0;
+
+  // Register an observer for when a certain |accelerator| is struck.
+  virtual void RegisterAccelerator(
+      const ui::Accelerator& accelerator, Observer* observer);
+  // Stop listening for the given |accelerator|.
+  virtual void UnregisterAccelerator(
+      const ui::Accelerator& accelerator, Observer* observer);
+
+ protected:
+  GlobalShortcutListener();
+
+  // Called by platform specific implementations of this class whenever a key

[Yoyo Zhou, 2013/10/04 18:12:07]

What I meant is here, it's only called for keys that have observers registered.

[Finnur, 2013/10/11 10:59:22]

Good point. Added that.

+  // is struck.
+  void NotifyKeyPressed(const ui::Accelerator& accelerator);
+
+  // The map of accelerators that have been successfully registered as global
+  // shortcuts and their observer lists.
+  typedef ObserverList<Observer> Observers;
+  typedef std::map< ui::Accelerator, Observers* > AcceleratorMap;
+  AcceleratorMap accelerator_map_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(GlobalShortcutListener);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_GLOBAL_SHORTCUT_LISTENER_H_