Convert drawPaint to drawRRect in simple cases

src/gpu/GrClipStackClip.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef GrClipStackClip_DEFINED
 #define GrClipStackClip_DEFINED
 
 #include "GrClip.h"
@@ skipping 20 matching lines @@
         fStack.reset(SkSafeRef(stack));
     }
 
     bool quickContains(const SkRect&) const final;
     bool quickContains(const SkRRect&) const final;
     void getConservativeBounds(int width, int height, SkIRect* devResult,
                                bool* isIntersectionOfRects) const final;
     bool apply(GrContext*, GrDrawContext*, bool useHWAA, bool hasUserStencilSettings,
                GrAppliedClip* out) const final;
 
+    bool isRRect(const SkRect& rtBounds, SkRRect* rr, bool* aa) const override;
+
 private:
     static bool PathNeedsSWRenderer(GrContext* context,
                                     bool hasUserStencilSettings,
                                     const GrDrawContext*,
                                     const SkMatrix& viewMatrix,
                                     const SkClipStack::Element* element,
                                     GrPathRenderer** prOut,
                                     bool needsStencil);
 
     // Draws the clip into the stencil buffer
@@ skipping 20 matching lines @@
                              const GrReducedClip::ElementList& elements);
 
     static GrTexture* CreateCachedMask(int width, int height, const GrUniqueKey& key,
                                        bool renderTarget);
 
     SkIPoint                          fOrigin;
     SkAutoTUnref<const SkClipStack>   fStack;
 };
 
 #endif // GrClipStackClip_DEFINED