Refactoring DrawLooper so that it can apply shadow effects as skia image filters

Source/core/rendering/RenderBoxModelObject.cpp

Index: Source/core/rendering/RenderBoxModelObject.cpp
diff --git a/Source/core/rendering/RenderBoxModelObject.cpp b/Source/core/rendering/RenderBoxModelObject.cpp
index f6a8072c3c4d6e6f78b87d92665eb4b2147668f9..b26b228618796a12e89d3f050e0c33fde1e2888f 100644
--- a/Source/core/rendering/RenderBoxModelObject.cpp
+++ b/Source/core/rendering/RenderBoxModelObject.cpp
@@ -2513,10 +2513,10 @@ void RenderBoxModelObject::paintBoxShadow(const PaintInfo& info, const LayoutRec
             }
 
             // Draw only the shadow.
-            DrawLooper drawLooper;
-            drawLooper.addShadow(shadowOffset, shadowBlur, shadowColor,
+            RefPtr<DrawLooper> drawLooper(new DrawLooper);
+            drawLooper->addShadow(shadowOffset, shadowBlur, shadowColor,
                 DrawLooper::ShadowRespectsTransforms, DrawLooper::ShadowIgnoresAlpha);
-            context->setDrawLooper(drawLooper);
+            context->setDrawLooper(drawLooper.release());
 
             if (hasBorderRadius) {
                 RoundedRect influenceRect(shadowRect, border.radii());