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

gm/rrectclipdrawpaint.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkPath.h"
 #include "SkGradientShader.h"
 
 // Exercises code in GrDrawContext that attempts to replace a rrect clip/draw paint with draw rrect.
 DEF_SIMPLE_GM(rrect_clip_draw_paint, canvas, 256, 256) {
     SkRRect rrect = SkRRect::MakeRectXY(SkRect::MakeXYWH(10.f, 10.f, 236.f, 236.f), 30.f, 40.f);
 
     SkPaint p;
     p.setColor(SK_ColorRED);
 
     SkMatrix zoomOut;
     zoomOut.setScale(0.7f, 0.7f, 128.f, 128.f);
 
     const SkRect layerRect = SkRect::MakeWH(256.f, 256.f);
     canvas->saveLayer(layerRect, nullptr);
-    canvas->clipRRect(rrect, SkCanvas::kIntersect_Op, true);
+    canvas->clipRRect(rrect, true);
     canvas->drawPaint(p);
     canvas->restore();
 
     canvas->concat(zoomOut);
     p.setColor(SK_ColorBLUE);
     canvas->saveLayer(layerRect, nullptr);
-    canvas->clipRRect(rrect, SkCanvas::kIntersect_Op, false);
+    canvas->clipRRect(rrect, false);
     canvas->drawPaint(p);
     canvas->restore();
 
     constexpr SkPoint kPts[] = {{0.f, 0.f}, {256.f, 256.f}};
     constexpr SkColor kColors1[] = {SK_ColorCYAN, SK_ColorGREEN};
     p.setShader(SkGradientShader::MakeLinear(kPts, kColors1, nullptr, 2,
                                              SkShader::kClamp_TileMode));
     canvas->concat(zoomOut);
     canvas->saveLayer(layerRect, nullptr);
-    canvas->clipRRect(rrect, SkCanvas::kIntersect_Op, true);
+    canvas->clipRRect(rrect, true);
     canvas->drawPaint(p);
     canvas->restore();
 
     constexpr SkColor kColors2[] = {SK_ColorMAGENTA, SK_ColorGRAY};
     p.setShader(SkGradientShader::MakeRadial({128.f, 128.f}, 128.f, kColors2, nullptr, 2,
                                              SkShader::kClamp_TileMode));
     canvas->concat(zoomOut);
     canvas->saveLayer(layerRect, nullptr);
-    canvas->clipRRect(rrect, SkCanvas::kIntersect_Op, false);
+    canvas->clipRRect(rrect, false);
     canvas->drawPaint(p);
     canvas->restore();
 }