Don't create a GXPFactory when blend is SrcOver

src/gpu/effects/GrConfigConversionEffect.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrConfigConversionEffect.h"
 #include "GrContext.h"
 #include "GrDrawContext.h"
@@ skipping 205 matching lines @@
         GrPaint paint2;
         GrPaint paint3;
         SkAutoTUnref<GrFragmentProcessor> pmToUPM1(new GrConfigConversionEffect(
                 dataTex, false, *pmToUPMRule, SkMatrix::I()));
         SkAutoTUnref<GrFragmentProcessor> upmToPM(new GrConfigConversionEffect(
                 readTex, false, *upmToPMRule, SkMatrix::I()));
         SkAutoTUnref<GrFragmentProcessor> pmToUPM2(new GrConfigConversionEffect(
                 tempTex, false, *pmToUPMRule, SkMatrix::I()));
 
         paint1.addColorFragmentProcessor(pmToUPM1);
+        paint1.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
 
 
         SkAutoTUnref<GrDrawContext> readDrawContext(
                                     context->drawContext(readTex->asRenderTarget()));
         if (!readDrawContext) {
             failed = true;
             break;
         }
 
         readDrawContext->fillRectToRect(GrClip::WideOpen(),
                                         paint1,
                                         SkMatrix::I(),
                                         kDstRect,
                                         kSrcRect);
 
         readTex->readPixels(0, 0, 256, 256, kRGBA_8888_GrPixelConfig, firstRead);
 
         paint2.addColorFragmentProcessor(upmToPM);
+        paint2.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
 
         SkAutoTUnref<GrDrawContext> tempDrawContext(
                                     context->drawContext(tempTex->asRenderTarget()));
         if (!tempDrawContext) {
             failed = true;
             break;
         }
         tempDrawContext->fillRectToRect(GrClip::WideOpen(),
                                         paint2,
                                         SkMatrix::I(),
                                         kDstRect,
                                         kSrcRect);
 
         paint3.addColorFragmentProcessor(pmToUPM2);
+        paint3.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
 
         readDrawContext.reset(context->drawContext(readTex->asRenderTarget()));
         if (!readDrawContext) {
             failed = true;
             break;
         }
 
         readDrawContext->fillRectToRect(GrClip::WideOpen(),
                                         paint3,
                                         SkMatrix::I(),
@@ skipping 30 matching lines @@
     } else {
         if (kRGBA_8888_GrPixelConfig != texture->config() &&
             kBGRA_8888_GrPixelConfig != texture->config() &&
             kNone_PMConversion != pmConversion) {
             // The PM conversions assume colors are 0..255
             return nullptr;
         }
         return new GrConfigConversionEffect(texture, swapRedAndBlue, pmConversion, matrix);
     }
 }