Make skpaint->grpaint flow work for composing draws

src/core/SkBitmapProcShader.cpp

Index: src/core/SkBitmapProcShader.cpp
diff --git a/src/core/SkBitmapProcShader.cpp b/src/core/SkBitmapProcShader.cpp
index 8a5e03cfc315848738387edf2646548aa0f42616..602e4e3e831adef4d6642b831d71e2c213f39b93 100644
--- a/src/core/SkBitmapProcShader.cpp
+++ b/src/core/SkBitmapProcShader.cpp
@@ -408,9 +408,9 @@ const GrFragmentProcessor* SkBitmapProcShader::asFragmentProcessor(GrContext* co
     }
 
     if (kAlpha_8_SkColorType == fRawBitmap.colorType()) {
-        return SkRef(inner.get());
+        return GrFragmentProcessor::MulOutputByInputUnpremulColor(inner);
     }
-    return GrFragmentProcessor::MulOuputByInputAlpha(inner);
+    return GrFragmentProcessor::MulOutputByInputAlpha(inner);
 }
 
 #endif