Don't create a GXPFactory when blend is SrcOver

gm/yuvtorgbeffect.cpp

 
 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 // This test only works with the GPU backend.
 
@@ skipping 97 matching lines @@
             renderRect.outset(kDrawPad, kDrawPad);
 
             SkScalar y = kDrawPad + kTestPad + space * kColorSpaceOffset;
             SkScalar x = kDrawPad + kTestPad;
 
             const int indices[6][3] = {{0, 1, 2}, {0, 2, 1}, {1, 0, 2},
                                        {1, 2, 0}, {2, 0, 1}, {2, 1, 0}};
 
             for (int i = 0; i < 6; ++i) {
                 GrPipelineBuilder pipelineBuilder;
+                pipelineBuilder.setXPFactory(
+                    GrPorterDuffXPFactory::Create(SkXfermode::kSrc_Mode))->unref();
                 SkAutoTUnref<GrFragmentProcessor> fp(
                             GrYUVtoRGBEffect::Create(texture[indices[i][0]],
                                                      texture[indices[i][1]],
                                                      texture[indices[i][2]],
                                                      sizes,
                                                      static_cast<SkYUVColorSpace>(space)));
                 if (fp) {
                     SkMatrix viewMatrix;
                     viewMatrix.setTranslate(x, y);
                     pipelineBuilder.setRenderTarget(rt);
@@ skipping 11 matching lines @@
 private:
     SkBitmap fBmp[3];
 
     typedef GM INHERITED;
 };
 
 DEF_GM(return new YUVtoRGBEffect;)
 }
 
 #endif