add new copyTo version to SkBitmap, which takes SkColorType

gm/bitmapfilters.cpp

Index: gm/bitmapfilters.cpp
diff --git a/gm/bitmapfilters.cpp b/gm/bitmapfilters.cpp
index 7addf25c012e263297f88fa4fa33b9207d13ab01..fb3b304eb973a9dc0cd4caec9c1ee0cf90d8554d 100644
--- a/gm/bitmapfilters.cpp
+++ b/gm/bitmapfilters.cpp
@@ -85,9 +85,9 @@ class FilterGM : public GM {
         }
         fOnce = true;
         make_bm(&fBM8);
-        fBM8.copyTo(&fBM4444, SkBitmap::kARGB_4444_Config);
-        fBM8.copyTo(&fBM16, SkBitmap::kRGB_565_Config);
-        fBM8.copyTo(&fBM32, SkBitmap::kARGB_8888_Config);
+        fBM8.copyTo(&fBM4444, kARGB_4444_SkColorType);
+        fBM8.copyTo(&fBM16, kRGB_565_SkColorType);
+        fBM8.copyTo(&fBM32, kPMColor_SkColorType);
     }
 public:
     SkBitmap    fBM8, fBM4444, fBM16, fBM32;