store SkAlphaType inside SkBitmap, on road to support unpremul

src/image/SkImage_Raster.cpp

Index: src/image/SkImage_Raster.cpp
diff --git a/src/image/SkImage_Raster.cpp b/src/image/SkImage_Raster.cpp
index cd9b70f018bc6637192dbcca4a581af1b47ffc93..b3ff7a6f616a665e9f01993ce80d7037372929a1 100644
--- a/src/image/SkImage_Raster.cpp
+++ b/src/image/SkImage_Raster.cpp
@@ -88,9 +88,9 @@ SkImage_Raster::SkImage_Raster(const Info& info, SkData* data, size_t rowBytes)
     bool isOpaque;
     SkBitmap::Config config = SkImageInfoToBitmapConfig(info, &isOpaque);
 
-    fBitmap.setConfig(config, info.fWidth, info.fHeight, rowBytes);
+    fBitmap.setConfig(config, info.fWidth, info.fHeight, rowBytes, isOpaque ?
+                      kOpaque_SkAlphaType : kPremul_SkAlphaType);
     fBitmap.setPixelRef(SkNEW_ARGS(SkDataPixelRef, (data)))->unref();
-    fBitmap.setIsOpaque(isOpaque);
     fBitmap.setImmutable();
 }
 
@@ -99,9 +99,9 @@ SkImage_Raster::SkImage_Raster(const Info& info, SkPixelRef* pr, size_t rowBytes
     bool isOpaque;
     SkBitmap::Config config = SkImageInfoToBitmapConfig(info, &isOpaque);
 
-    fBitmap.setConfig(config, info.fWidth, info.fHeight, rowBytes);
+    fBitmap.setConfig(config, info.fWidth, info.fHeight, rowBytes, isOpaque ?
+                      kOpaque_SkAlphaType : kPremul_SkAlphaType);
     fBitmap.setPixelRef(pr);
-    fBitmap.setIsOpaque(isOpaque);
 }
 
 SkImage_Raster::~SkImage_Raster() {}