First pass at removal of unneeded dependencies on skia\ext\platform_canvas.h

All 'low-hanging' platform_canvas.h dependencies have been removed, and replaced with skia-specific includes.

BUG=None
TEST=None
Review URL: http://codereview.chromium.org/7517020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@95083 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/ui/gfx/canvas.h b/ui/gfx/canvas.h
index 2d2a55ba..5e32cd2 100644
--- a/ui/gfx/canvas.h
+++ b/ui/gfx/canvas.h
@@ -9,8 +9,9 @@
 #include <string>
 
 #include "base/string16.h"
-// TODO(beng): remove this include when we no longer depend on SkTypes.
-#include "skia/ext/platform_canvas.h"
+// TODO(beng): remove these includes when we no longer depend on SkTypes.
+#include "third_party/skia/include/core/SkColor.h"
+#include "third_party/skia/include/core/SkXfermode.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/ui_api.h"