allow clip calls w/o op param, remove unnecessary kReplace ops

gm/rrects.cpp

Index: gm/rrects.cpp
diff --git a/gm/rrects.cpp b/gm/rrects.cpp
index 46c1c67072c62431d762dfc07928a74390f14f4a..1f47f77daa80170aba8f594903116cdda4b8ce51 100644
--- a/gm/rrects.cpp
+++ b/gm/rrects.cpp
@@ -124,7 +124,7 @@ protected:
 #endif
                     } else if (kBW_Clip_Type == fType || kAA_Clip_Type == fType) {
                         bool aaClip = (kAA_Clip_Type == fType);
-                        canvas->clipRRect(fRRects[curRRect], SkCanvas::kReplace_Op, aaClip);
+                        canvas->clipRRect(fRRects[curRRect], aaClip);
                         canvas->drawRect(kMaxTileBound, paint);
                     } else {
                         canvas->drawRRect(fRRects[curRRect], paint);