Specialize GrConvexPolyEffect for AA rects, use for AA clip rects.

src/gpu/effects/GrConvexPolyEffect.h

Index: src/gpu/effects/GrConvexPolyEffect.h
diff --git a/src/gpu/effects/GrConvexPolyEffect.h b/src/gpu/effects/GrConvexPolyEffect.h
index 225e729242a339a22094080cb7f61a4ea0043977..d7d17ab35acea7ef74e4d752b45ea4a75fcd7849 100644
--- a/src/gpu/effects/GrConvexPolyEffect.h
+++ b/src/gpu/effects/GrConvexPolyEffect.h
@@ -62,6 +62,11 @@ public:
      */
     static GrEffectRef* Create(EdgeType, const SkPath&, const SkVector* offset= NULL);
 
+    /**
+     * Creates an effect that fills inside the rect with AA edges..
+     */
+    static GrEffectRef* CreateForAAFillRect(const SkRect&);
+
     virtual ~GrConvexPolyEffect();
 
     static const char* Name() { return "ConvexPoly"; }