Make all blending up to GrOptDrawState be handled by the xp/xp factory.

src/effects/SkAlphaThresholdFilter.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 "SkAlphaThresholdFilter.h"
 #include "SkBitmap.h"
 #include "SkReadBuffer.h"
@@ skipping 30 matching lines @@
                                               SkImageFilter* input) {
     return SkNEW_ARGS(SkAlphaThresholdFilterImpl, (region, innerThreshold, outerThreshold, input));
 }
 
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
 #include "GrCoordTransform.h"
 #include "GrFragmentProcessor.h"
 #include "GrInvariantOutput.h"
 #include "GrTextureAccess.h"
+#include "effects/GrPorterDuffXferProcessor.h"
 
 #include "SkGr.h"
 
 #include "gl/GrGLProcessor.h"
 #include "gl/builders/GrGLProgramBuilder.h"
 
 class AlphaThresholdEffect : public GrFragmentProcessor {
 
 public:
     static GrFragmentProcessor* Create(GrTexture* texture,
@@ skipping 213 matching lines @@
         maskDesc.fHeight = texture->height();
         SkAutoTUnref<GrTexture> maskTexture(
             context->refScratchTexture(maskDesc, GrContext::kApprox_ScratchTexMatch));
         if (!maskTexture) {
             return false;
         }
 
         {
             GrContext::AutoRenderTarget art(context, maskTexture->asRenderTarget());
             GrPaint grPaint;
-            grPaint.setBlendFunc(kOne_GrBlendCoeff, kZero_GrBlendCoeff);
+            grPaint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
             SkRegion::Iterator iter(fRegion);
             context->clear(NULL, 0x0, true, maskTexture->asRenderTarget());
 
             SkMatrix old_matrix = context->getMatrix();
             context->setMatrix(in_matrix);
 
             while (!iter.done()) {
                 SkRect rect = SkRect::Make(iter.rect());
                 context->drawRect(grPaint, rect);
                 iter.next();
@@ skipping 71 matching lines @@
                                                   (U8CPU)(SkColorGetG(source) * scale),
                                                   (U8CPU)(SkColorGetB(source) * scale));
                 }
             }
             dptr[y * dst->width() + x] = output_color;
         }
     }
 
     return true;
 }