ash: Avoid implicit conversion from ImageSkia into SkBitmap.

ash/desktop_background/desktop_background_controller.h

Index: ash/desktop_background/desktop_background_controller.h
diff --git a/ash/desktop_background/desktop_background_controller.h b/ash/desktop_background/desktop_background_controller.h
index edcd803a2f28e923301e6f9e8ecced9e8feda304..048b8accb6dcb7ee87f73ca2a9a97005d4eaef9f 100644
--- a/ash/desktop_background/desktop_background_controller.h
+++ b/ash/desktop_background/desktop_background_controller.h
@@ -11,13 +11,13 @@
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
-#include "third_party/skia/include/core/SkBitmap.h"
-#include "third_party/skia/include/core/SkColor.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_observer.h"
 #include "ui/compositor/layer.h"
 #include "ui/gfx/image/image_skia.h"
 
+typedef unsigned int SkColor;
+
 namespace aura {
 class RootWindow;
 }
@@ -69,9 +69,9 @@ class ASH_EXPORT DesktopBackgroundController : public aura::WindowObserver {
 
   WallpaperLayout GetWallpaperLayout() const;
 
-  // Provides current image on the background, or empty SkBitmap if there is
-  // no image, e.g. background is solid color.
-  SkBitmap GetCurrentWallpaperImage();
+  // Provides current image on the background, or empty gfx::ImageSkia if there
+  // is no image, e.g. background is solid color.
+  gfx::ImageSkia GetCurrentWallpaperImage();
 
   // Initialize root window's background.
   void OnRootWindowAdded(aura::RootWindow* root_window);