Fixed Shadow blur for transparent objects

Source/platform/graphics/UnacceleratedImageBufferSurface.cpp

Index: Source/platform/graphics/UnacceleratedImageBufferSurface.cpp
diff --git a/Source/platform/graphics/UnacceleratedImageBufferSurface.cpp b/Source/platform/graphics/UnacceleratedImageBufferSurface.cpp
index 35ea4f7cd49b69cc1ee56f43d449cf600363dcaa..b4644d4d117966127074844dd71752fd3cda6e1e 100644
--- a/Source/platform/graphics/UnacceleratedImageBufferSurface.cpp
+++ b/Source/platform/graphics/UnacceleratedImageBufferSurface.cpp
@@ -38,8 +38,11 @@ namespace blink {
 
 UnacceleratedImageBufferSurface::UnacceleratedImageBufferSurface(const IntSize& size, OpacityMode opacityMode)
     : ImageBufferSurface(size, opacityMode)
-    , m_surface(adoptRef(SkSurface::NewRasterPMColor(size.width(), size.height())))
 {
+    SkAlphaType alphaType = (Opaque == opacityMode) ? kOpaque_SkAlphaType : kPremul_SkAlphaType;
+    SkImageInfo info = SkImageInfo::MakeN32(size.width(), size.height(), alphaType);
+    m_surface = adoptRef(SkSurface::NewRaster(info));
+
     if (m_surface)
         clear();
 }