Make SkBitmap::CopyTo respect requested dst color type when bitmap is texture backed.

include/core/SkPixelRef.h

Index: include/core/SkPixelRef.h
diff --git a/include/core/SkPixelRef.h b/include/core/SkPixelRef.h
index 4591ed82bffbba14fde355ab56ceb1c2cdadb3b1..9cdcd85a798b5faf5f27c809fb8b07292d10848a 100644
--- a/include/core/SkPixelRef.h
+++ b/include/core/SkPixelRef.h
@@ -225,7 +225,8 @@ public:
         return this->onGetYUV8Planes(sizes, planes, rowBytes, colorSpace);
     }
 
-    bool readPixels(SkBitmap* dst, const SkIRect* subset = NULL);
+    /** Populates dst with the pixels of this pixelRef, converting them to colorType. */
+    bool readPixels(SkBitmap* dst, SkColorType colorType, const SkIRect* subset = NULL);
 
     /**
      *  Makes a deep copy of this PixelRef, respecting the requested config.
@@ -299,7 +300,7 @@ protected:
      *
      *  The base class implementation returns false;
      */
-    virtual bool onReadPixels(SkBitmap* dst, const SkIRect* subsetOrNull);
+    virtual bool onReadPixels(SkBitmap* dst, SkColorType colorType, const SkIRect* subsetOrNull);
 
     // default impl returns NULL.
     virtual SkData* onRefEncodedData();