store SkAlphaType inside SkBitmap, on road to support unpremul

src/lazy/SkLazyPixelRef.cpp

Index: src/lazy/SkLazyPixelRef.cpp
diff --git a/src/lazy/SkLazyPixelRef.cpp b/src/lazy/SkLazyPixelRef.cpp
index 9e023c4a7c8859369886fe07a650c85fe1c69e23..f322c9324dd3ee7ef31a75bea53364061d1ca1cf 100644
--- a/src/lazy/SkLazyPixelRef.cpp
+++ b/src/lazy/SkLazyPixelRef.cpp
@@ -156,9 +156,10 @@ static bool init_from_info(SkBitmap* bm, const SkImage::Info& info,
         return false;
     }
 
-    bm->setConfig(config, info.fWidth, info.fHeight, rowBytes);
-    bm->setIsOpaque(isOpaque);
-    return bm->allocPixels();
+    return bm->setConfig(config, info.fWidth, info.fHeight, rowBytes,
+                  isOpaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType)
+           &&
+           bm->allocPixels();
 }
 
 bool SkLazyPixelRef::onImplementsDecodeInto() {