Don't create a GXPFactory when blend is SrcOver

src/effects/SkGpuBlurUtils.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGpuBlurUtils.h"
 
 #include "SkRect.h"
@@ skipping 41 matching lines @@
                                  GrTexture* texture,
                                  Gr1DKernelEffect::Direction direction,
                                  int radius,
                                  float sigma,
                                  bool useBounds,
                                  float bounds[2]) {
     GrPaint paint;
     SkAutoTUnref<GrFragmentProcessor> conv(GrConvolutionEffect::CreateGaussian(
         texture, direction, radius, sigma, useBounds, bounds));
     paint.addColorFragmentProcessor(conv);
+    paint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
     SkMatrix localMatrix = SkMatrix::MakeTrans(srcOffset.x(), srcOffset.y());
     drawContext->fillRectWithLocalMatrix(clip, paint, SkMatrix::I(), dstRect, localMatrix);
 }
 
 static void convolve_gaussian_2d(GrDrawContext* drawContext,
                                  const GrClip& clip,
                                  const SkRect& srcRect,
                                  GrTexture* texture,
                                  int radiusX,
                                  int radiusY,
@@ skipping 10 matching lines @@
         srcBounds->roundOut(&bounds);
     } else {
         bounds.setEmpty();
     }
 
     SkAutoTUnref<GrFragmentProcessor> conv(GrMatrixConvolutionEffect::CreateGaussian(
             texture, bounds, size, 1.0, 0.0, kernelOffset,
             srcBounds ? GrTextureDomain::kDecal_Mode : GrTextureDomain::kIgnore_Mode,
             true, sigmaX, sigmaY));
     paint.addColorFragmentProcessor(conv);
+    paint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
     drawContext->fillRectWithLocalMatrix(clip, paint, SkMatrix::I(), dstRect, localMatrix);
 }
 
 static void convolve_gaussian(GrDrawContext* drawContext,
                               const GrClip& clip,
                               const SkRect& srcRect,
                               GrTexture* texture,
                               Gr1DKernelEffect::Direction direction,
                               int radius,
                               float sigma,
@@ skipping 138 matching lines @@
                 domain,
                 GrTextureDomain::kDecal_Mode,
                 GrTextureParams::kBilerp_FilterMode));
             paint.addColorFragmentProcessor(fp);
             srcRect.offset(-srcOffset);
             srcOffset.set(0, 0);
         } else {
             GrTextureParams params(SkShader::kClamp_TileMode, GrTextureParams::kBilerp_FilterMode);
             paint.addColorTextureProcessor(srcTexture, matrix, params);
         }
+        paint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
         scale_rect(&dstRect, i < scaleFactorX ? 0.5f : 1.0f,
                              i < scaleFactorY ? 0.5f : 1.0f);
 
         SkAutoTUnref<GrDrawContext> dstDrawContext(
                                              context->drawContext(dstTexture->asRenderTarget()));
         if (!dstDrawContext) {
             return nullptr;
         }
         dstDrawContext->fillRectToRect(clip, paint, SkMatrix::I(), dstRect, srcRect);
 
@@ skipping 107 matching lines @@
         clearRect = SkIRect::MakeXYWH(srcIRect.fRight, srcIRect.fTop,
                                       1, srcIRect.height());
         srcDrawContext->clear(&clearRect, 0x0, false);
         SkMatrix matrix;
         matrix.setIDiv(srcTexture->width(), srcTexture->height());
 
         GrPaint paint;
         // FIXME:  this should be mitchell, not bilinear.
         GrTextureParams params(SkShader::kClamp_TileMode, GrTextureParams::kBilerp_FilterMode);
         paint.addColorTextureProcessor(srcTexture, matrix, params);
+        paint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
 
         SkRect dstRect(srcRect);
         scale_rect(&dstRect, (float) scaleFactorX, (float) scaleFactorY);
 
         SkAutoTUnref<GrDrawContext> dstDrawContext(
                                 context->drawContext(dstTexture->asRenderTarget()));
         if (!dstDrawContext) {
             return nullptr;
         }
         dstDrawContext->fillRectToRect(clip, paint, SkMatrix::I(), dstRect, srcRect);
 
         srcDrawContext.swap(dstDrawContext);
         srcRect = dstRect;
         srcTexture = dstTexture;
         SkTSwap(dstTexture, tempTexture);
     }
 
     return SkRef(srcTexture);
 }
 #endif
 
 }