add new copyTo version to SkBitmap, which takes SkColorType

src/utils/mac/SkCreateCGImageRef.cpp

Index: src/utils/mac/SkCreateCGImageRef.cpp
diff --git a/src/utils/mac/SkCreateCGImageRef.cpp b/src/utils/mac/SkCreateCGImageRef.cpp
index 01f2dacdda44116fb8480e41696120ce56e9a96f..7687c3c7e4a05b4688977eddf10719577ab714a9 100644
--- a/src/utils/mac/SkCreateCGImageRef.cpp
+++ b/src/utils/mac/SkCreateCGImageRef.cpp
@@ -94,7 +94,7 @@ static SkBitmap* prepareForImageRef(const SkBitmap& bm,
         copy = new SkBitmap;
         // here we make a ceep copy of the pixels, since CG won't take our
         // 565 directly
-        bm.copyTo(copy, SkBitmap::kARGB_8888_Config);
+        bm.copyTo(copy, kPMColor_SkColorType);
     } else {
         copy = new SkBitmap(bm);
     }