Don't create a GXPFactory when blend is SrcOver

src/effects/SkLightingImageFilter.cpp

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLightingImageFilter.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
@@ skipping 336 matching lines @@
                                              GrTexture* src,
                                              const SkMatrix& matrix,
                                              const GrClip& clip,
                                              const SkRect& dstRect,
                                              BoundaryMode boundaryMode,
                                              const SkIRect& bounds) const {
     SkRect srcRect = dstRect.makeOffset(SkIntToScalar(bounds.x()), SkIntToScalar(bounds.y()));
     GrPaint paint;
     GrFragmentProcessor* fp = this->getFragmentProcessor(src, matrix, bounds, boundaryMode);
     paint.addColorFragmentProcessor(fp)->unref();
+    paint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
     drawContext->fillRectToRect(clip, paint, SkMatrix::I(), dstRect, srcRect);
 }
 
 bool SkLightingImageFilterInternal::filterImageGPU(Proxy* proxy,
                                                    const SkBitmap& src,
                                                    const Context& ctx,
                                                    SkBitmap* result,
                                                    SkIPoint* offset) const {
     SkBitmap input = src;
     SkIPoint srcOffset = SkIPoint::Make(0, 0);
@@ skipping 1661 matching lines @@
 
     fragBuilder->codeAppendf("%s(%s)", fLightColorFunc.c_str(), surfaceToLight);
 }
 
 #endif
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkLightingImageFilter)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkDiffuseLightingImageFilter)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkSpecularLightingImageFilter)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END