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

gm/aaclip.cpp

 /*
  * Copyright 2011 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 "SkCanvas.h"
 #include "SkPath.h"
@@ skipping 67 matching lines @@
     SkPaint foregroundPaint;
     foregroundPaint.setColor(SkColorSetRGB(0x0, 0x0, 0xDD));
     foregroundPaint.setAntiAlias(true);
 
     canvas->save();
     canvas->translate(SkIntToScalar(x), SkIntToScalar(y));
     target.inset(SkIntToScalar(-2), SkIntToScalar(-2));
     canvas->drawRect(target, borderPaint);
     target.inset(SkIntToScalar(2), SkIntToScalar(2));
     canvas->drawRect(target, backgroundPaint);
-    canvas->clipRect(target, SkCanvas::kIntersect_Op, true);
+    canvas->clipRect(target, true);
     target.inset(SkIntToScalar(-4), SkIntToScalar(-4));
     canvas->drawRect(target, foregroundPaint);
     canvas->restore();
 }
 
 static void draw_square(SkCanvas* canvas, int x, int y) {
     SkRect target (SkRect::MakeWH(10 * SK_Scalar1, 10 * SK_Scalar1));
     draw(canvas, target, x, y);
 }
 
@@ skipping 210 matching lines @@
         canvas->translate(80, 10);
         this->drawAndClip(canvas, fVPath, 200, 0);
         canvas->translate(0, 200);
         this->drawAndClip(canvas, fHPath, 200, 0);
     }
 
 private:
     typedef skiagm::GM INHERITED;
 };
 DEF_GM(return new ClipCubicGM;)