Remove include of RetainPtr.h in Image.h.

This file does not use RetainPtr.

Review URL: https://codereview.chromium.org/1309283002

git-svn-id: svn://svn.chromium.org/blink/trunk@201197 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/platform/graphics/Image.h

@@ -38,7 +38,6 @@
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
-#include "wtf/RetainPtr.h"
 #include "wtf/text/WTFString.h"
 
 class SkBitmap;