store SkAlphaType inside SkBitmap, on road to support unpremul

src/image/SkSurface_Raster.cpp

Index: src/image/SkSurface_Raster.cpp
diff --git a/src/image/SkSurface_Raster.cpp b/src/image/SkSurface_Raster.cpp
index ccfdd27b1cb82cab885098ca458c2f5ffd07cfa9..3835c3b36cace407f968fbb7ce1b95e4ad5df0f8 100644
--- a/src/image/SkSurface_Raster.cpp
+++ b/src/image/SkSurface_Raster.cpp
@@ -86,9 +86,9 @@ SkSurface_Raster::SkSurface_Raster(const SkImage::Info& info, void* pixels, size
     bool isOpaque;
     SkBitmap::Config config = SkImageInfoToBitmapConfig(info, &isOpaque);
 
-    fBitmap.setConfig(config, info.fWidth, info.fHeight, rb);
+    fBitmap.setConfig(config, info.fWidth, info.fHeight, rb, isOpaque ?
+                      kOpaque_SkAlphaType : kPremul_SkAlphaType);
     fBitmap.setPixels(pixels);
-    fBitmap.setIsOpaque(isOpaque);
     fWeOwnThePixels = false;    // We are "Direct"
 }
 
@@ -97,9 +97,9 @@ SkSurface_Raster::SkSurface_Raster(const SkImage::Info& info, SkPixelRef* pr, si
     bool isOpaque;
     SkBitmap::Config config = SkImageInfoToBitmapConfig(info, &isOpaque);
 
-    fBitmap.setConfig(config, info.fWidth, info.fHeight, rb);
+    fBitmap.setConfig(config, info.fWidth, info.fHeight, rb, isOpaque ?
+                      kOpaque_SkAlphaType : kPremul_SkAlphaType);
     fBitmap.setPixelRef(pr);
-    fBitmap.setIsOpaque(isOpaque);
     fWeOwnThePixels = true;
 
     if (!isOpaque) {