Magnifier: Prevent useless operation in enabling/disabling magnifier.

chrome/browser/chromeos/accessibility/magnification_manager.h

Index: chrome/browser/chromeos/accessibility/magnification_manager.h
diff --git a/chrome/browser/chromeos/accessibility/magnification_manager.h b/chrome/browser/chromeos/accessibility/magnification_manager.h
index 29529b5b647fbbbb7b78f21e0df909204022bf8c..a5f3f51ac73c3399a3f4b3ac200544cc1a33d50f 100644
--- a/chrome/browser/chromeos/accessibility/magnification_manager.h
+++ b/chrome/browser/chromeos/accessibility/magnification_manager.h
@@ -9,6 +9,11 @@
 
 namespace chromeos {
 
+class MagnificationObserver {
+ public:
+  virtual void OnMagnifierTypeChanged(ash::MagnifierType new_type) = 0;
+};
+
 // MagnificationManager controls the full screen magnifier from chrome-browser
 // side (not ash side).
 //
@@ -20,14 +25,15 @@ namespace chromeos {
 
 class MagnificationManager {
  public:
-  // Creates an instance of MagnificationManager. This should be called once,
-  // because only one instance should exist at the same time.
-  static MagnificationManager* CreateInstance();
-  // Returns the existing instance. If there is no instance, returns NULL.
+  // Returns the existing instance. If there is no instance, creates one.
   static MagnificationManager* GetInstance();
 
+  virtual void Initialize() = 0;
   virtual ~MagnificationManager() {}

[stevenjb, 2012/12/04 01:35:34]

nit: This should be protected

[yoshiki, 2012/12/04 08:30:20]

Done.

 
+  virtual void AddObserver(MagnificationObserver* observer) = 0;
+  virtual void RemoveObserver(MagnificationObserver* observer) = 0;
+
   // Returns the current type of the screen magnifier.
   virtual ash::MagnifierType GetMagnifierType() = 0;
   // Changes the type of the screen magnifier.