Added const to image parameters for ImageButton class.

views/controls/button/image_button.h

Index: views/controls/button/image_button.h
===================================================================
--- views/controls/button/image_button.h	(revision 48732)
+++ views/controls/button/image_button.h	(working copy)
@@ -22,10 +22,12 @@
   virtual ~ImageButton();
 
   // Set the image the button should use for the provided state.
-  virtual void SetImage(ButtonState aState, SkBitmap* anImage);
+  virtual void SetImage(ButtonState aState, const SkBitmap* anImage);
 
   // Set the background details.
-  virtual void SetBackground(SkColor color, SkBitmap* image, SkBitmap* mask);
+  void SetBackground(SkColor color,
+                     const SkBitmap* image,
+                     const SkBitmap* mask);
 
   enum HorizontalAlignment { ALIGN_LEFT = 0,
                              ALIGN_CENTER,
@@ -77,16 +79,16 @@
   // Change the toggled state.
   void SetToggled(bool toggled);
 
-  // Like Button::SetImage(), but to set the graphics used for the
+  // Like ImageButton::SetImage(), but to set the graphics used for the
   // "has been toggled" state.  Must be called for each button state
   // before the button is toggled.
-  void SetToggledImage(ButtonState state, SkBitmap* image);
+  void SetToggledImage(ButtonState state, const SkBitmap* image);
 
   // Set the tooltip text displayed when the button is toggled.
   void SetToggledTooltipText(const std::wstring& tooltip);
 
   // Overridden from ImageButton:
-  virtual void SetImage(ButtonState aState, SkBitmap* anImage);
+  virtual void SetImage(ButtonState aState, const SkBitmap* anImage);
 
   // Overridden from View:
   virtual bool GetTooltipText(const gfx::Point& p, std::wstring* tooltip);