leave pixel memory uninitialized for opaque alpha type in SkSurface::MakeRaster

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 f2cb94a04f75f48501a362cf840e3d9fee741504..2b2bf645260e2b3fc983ba1b6d0f638627b27849 100644
--- a/src/image/SkSurface_Raster.cpp
+++ b/src/image/SkSurface_Raster.cpp
@@ -208,7 +208,11 @@ sk_sp<SkSurface> SkSurface::MakeRaster(const SkImageInfo& info, size_t rowBytes,
         return nullptr;
     }
 
-    SkAutoTUnref<SkPixelRef> pr(SkMallocPixelRef::NewZeroed(info, rowBytes, nullptr));
+    // If the requested alpha type is opaque, then leave the pixels uninitialized.
+    // Alpha formats can be safely initialiezd to zero.
+    SkAutoTUnref<SkPixelRef> pr(info.isOpaque()
+                                ? SkMallocPixelRef::NewAllocate(info, rowBytes, nullptr)
+                                : SkMallocPixelRef::NewZeroed(info, rowBytes, nullptr));
     if (nullptr == pr.get()) {
         return nullptr;
     }