Add an option to create unpremultiplied bitmaps.

src/images/SkScaledBitmapSampler.h

Index: src/images/SkScaledBitmapSampler.h
diff --git a/src/images/SkScaledBitmapSampler.h b/src/images/SkScaledBitmapSampler.h
index 1466309a77bf62ed9a1196daf023ca43c2cef7fb..6477db2178641d0a6c2ad54bd34f6fb269ad315e 100644
--- a/src/images/SkScaledBitmapSampler.h
+++ b/src/images/SkScaledBitmapSampler.h
@@ -36,7 +36,7 @@ public:
     // prepares iterator to process the src colors and write them into dst.
     // Returns false if the request cannot be fulfulled.
     bool begin(SkBitmap* dst, SrcConfig sc, bool doDither,
-               const SkPMColor* = NULL);
+               const SkPMColor* = NULL, bool requireUnPremul = false);
     // call with row of src pixels, for y = 0...scaledHeight-1.
     // returns true if the row had non-opaque alpha in it
     bool next(const uint8_t* SK_RESTRICT src);