Implement first part of supporting global extension commands.

chrome/browser/extensions/global_shortcut_listener_mac.h

Index: chrome/browser/extensions/global_shortcut_listener_mac.h
diff --git a/chrome/browser/extensions/global_shortcut_listener_mac.h b/chrome/browser/extensions/global_shortcut_listener_mac.h
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+++ b/chrome/browser/extensions/global_shortcut_listener_mac.h
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+// 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_MAC_H_
+#define CHROME_BROWSER_EXTENSIONS_GLOBAL_SHORTCUT_LISTENER_MAC_H_
+
+#include "base/lazy_instance.h"
+#include "chrome/browser/extensions/global_shortcut_listener.h"
+
+namespace extensions {
+
+// Mac-specific implementation of the GlobalShortcutListener class that
+// listens for global shortcuts. Handles basic keyboard intercepting and
+// forwards its output to the base class for processing.
+// TODO(finnur/smus): Implement this class.
+class GlobalShortcutListenerMac : public GlobalShortcutListener {
+ public:
+  virtual ~GlobalShortcutListenerMac();
+
+  virtual void StartListening() OVERRIDE;
+  virtual void StopListening() OVERRIDE;
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<GlobalShortcutListenerMac>;
+
+  GlobalShortcutListenerMac();
+
+  // Register an |accelerator| with the particular |observer|.
+  virtual void RegisterAccelerator(
+      const ui::Accelerator& accelerator,
+      GlobalShortcutListener::Observer* observer) OVERRIDE;
+  // Unregister an |accelerator| with the particular |observer|.
+  virtual void UnregisterAccelerator(
+      const ui::Accelerator& accelerator,
+      GlobalShortcutListener::Observer* observer) OVERRIDE;
+
+  // Whether this object is listening for global shortcuts.
+  bool is_listening_;
+
+  DISALLOW_COPY_AND_ASSIGN(GlobalShortcutListenerMac);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_GLOBAL_SHORTCUT_LISTENER_MAC_H_