Refactor GlobalShortcutListener.

chrome/browser/extensions/global_shortcut_listener.h

Index: chrome/browser/extensions/global_shortcut_listener.h
diff --git a/chrome/browser/extensions/global_shortcut_listener.h b/chrome/browser/extensions/global_shortcut_listener.h
index c61abe65f0c16b91c722c33a1c9b165583e20af3..f79187440749231c72a06b65234fbf9e8b782ae0 100644
--- a/chrome/browser/extensions/global_shortcut_listener.h
+++ b/chrome/browser/extensions/global_shortcut_listener.h
@@ -18,7 +18,7 @@ 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
+// monitors keystrokes. It relays messages to the appropriate observer when a
 // global shortcut has been struck by the user.
 class GlobalShortcutListener {
  public:
@@ -32,28 +32,32 @@ class 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);
+  // Register an observer for when a certain |accelerator| is struck. Return
+  // true if register successfully, false if the specificied |accelerator| has
+  // been registered by callers or other native applications.
+  bool RegisterAccelerator(const ui::Accelerator& accelerator,
+                           Observer* observer);
   // Stop listening for the given |accelerator|.
-  virtual void UnregisterAccelerator(
-      const ui::Accelerator& accelerator, Observer* observer);
+  void UnregisterAccelerator(const ui::Accelerator& accelerator,
+                             Observer* observer);
 
  protected:
   GlobalShortcutListener();
 
   // Called by platform specific implementations of this class whenever a key
-  // is struck. Only called for keys that have observers registered.
+  // is struck. Only called for keys that have an observer registered.
   void NotifyKeyPressed(const ui::Accelerator& accelerator);
 
+  // Implemented by platform-specific implementations of this class.
+  virtual void StartListening() = 0;
+  virtual void StopListening() = 0;
+  virtual bool RegisterAcceleratorImpl(const ui::Accelerator& accelerator) = 0;
+  virtual void UnregisterAcceleratorImpl(
+      const ui::Accelerator& accelerator) = 0;
+
   // 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;
+  // shortcuts and their observer.
+  typedef std::map< ui::Accelerator, Observer* > AcceleratorMap;
   AcceleratorMap accelerator_map_;
 
  private: