Add the partial screen magnifier to Chrome OS.

ash/magnifier/magnification_controller.h

 // Copyright (c) 2012 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 ASH_MAGNIFIER_MAGNIFICATION_CONTROLLER_H_
 #define ASH_MAGNIFIER_MAGNIFICATION_CONTROLLER_H_
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 12 matching lines @@
  public:
   virtual ~MagnificationController() {}
 
   // Creates a new MagnificationController. The caller takes ownership of the
   // returned object.
   static MagnificationController* CreateInstance();
 
   // Enables (or disables if |enabled| is false) screen magnifier feature.
   virtual void SetEnabled(bool enabled) = 0;
 
+  virtual bool IsEnabled() = 0;
+
   // Sets the magnification ratio. 1.0f means no magnification.
   virtual void SetScale(float scale, bool animate) = 0;
   // Returns the current magnification ratio.
   virtual float GetScale() const = 0;
 
   // Set the top-left point of the magnification window.
   virtual void MoveWindow(int x, int y, bool animate) = 0;
   virtual void MoveWindow(const gfx::Point& point, bool animate) = 0;
   // Returns the current top-left point of the magnification window.
   virtual gfx::Point GetWindowPosition() const = 0;
 
   // Ensures that the given point/rect is inside the magnification window. If
   // not, the controller moves the window to contain the given point/rect.
   virtual void EnsureRectIsVisible(const gfx::Rect& rect, bool animate) = 0;
   virtual void EnsurePointIsVisible(const gfx::Point& point, bool animate) = 0;
 
  protected:
   MagnificationController() {}
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_MAGNIFIER_MAGNIFICATION_CONTROLLER_H_