Add the partial screen magnifier to Chrome OS.

ash/magnifier/magnification_controller.h

Index: ash/magnifier/magnification_controller.h
diff --git a/ash/magnifier/magnification_controller.h b/ash/magnifier/magnification_controller.h
index 4b0e86540c33fd6f1a67d7cc201c3e0f00b2e2ec..6b5e3d169c6841770de43013300c968a07167723 100644
--- a/ash/magnifier/magnification_controller.h
+++ b/ash/magnifier/magnification_controller.h
@@ -17,7 +17,6 @@ class RootWindow;
 }
 
 namespace ash {
-namespace internal {
 
 class MagnificationController {
  public:
@@ -30,6 +29,8 @@ class MagnificationController {
   // Enables (or disables if |enabled| is false) screen magnifier feature.
   virtual void SetEnabled(bool enabled) = 0;
 
+  virtual bool IsEnabled() const = 0;
+
   // Sets the magnification ratio. 1.0f means no magnification.
   virtual void SetScale(float scale, bool animate) = 0;
   // Returns the current magnification ratio.
@@ -50,7 +51,6 @@ class MagnificationController {
   MagnificationController() {}
 };
 
-}  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_MAGNIFIER_MAGNIFICATION_CONTROLLER_H_