Don't create a GXPFactory when blend is SrcOver

gm/bigrrectaaeffect.cpp

 /*
  * Copyright 2015 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"
 #if SK_SUPPORT_GPU
 #include "GrTest.h"
@@ skipping 53 matching lines @@
 #endif
                 canvas->save();
                     canvas->translate(SkIntToScalar(x), SkIntToScalar(y));
                     GrTestTarget tt;
                     context->getTestTarget(&tt, rt);
                     if (nullptr == tt.target()) {
                         SkDEBUGFAIL("Couldn't get Gr test target.");
                         return;
                     }
                     GrPipelineBuilder pipelineBuilder;
+                    pipelineBuilder.setXPFactory(
+                        GrPorterDuffXPFactory::Create(SkXfermode::kSrc_Mode))->unref();
 
                     SkRRect rrect = fRRects[curRRect];
                     rrect.offset(SkIntToScalar(x), SkIntToScalar(y));
                     SkAutoTUnref<GrFragmentProcessor> fp(GrRRectEffect::Create(edgeType, rrect));
                     SkASSERT(fp);
                     if (fp) {
                         pipelineBuilder.addCoverageFragmentProcessor(fp);
                         pipelineBuilder.setRenderTarget(rt);
 
                         SkRect bounds = SkRect::MakeWH(SkIntToScalar(kMaxSize),
@@ skipping 39 matching lines @@
     SkTDArray<SkRRect> fRRects;
     typedef GM INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return new BigRRectAAEffectGM (); )
 
 }
 #endif