Implement support for KHR_blend_equation_advanced

src/gpu/GrXferProcessor.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 "GrXferProcessor.h"
 #include "gl/GrGLCaps.h"
 
@@ skipping 24 matching lines @@
 bool GrXferProcessor::willNeedXferBarrier(const GrRenderTarget* rt,
                                           const GrDrawTargetCaps& caps,
                                           GrXferBarrierType* outBarrierType) const {
     if (static_cast<const GrSurface*>(rt) == this->getDstCopyTexture()) {
         // Texture barriers are required when a shader reads and renders to the same texture.
         SkASSERT(rt);
         SkASSERT(caps.textureBarrierSupport());
         *outBarrierType = kTexture_GrXferBarrierType;
         return true;
     }
-    return false;
+    return this->onWillNeedXferBarrier(rt, caps, outBarrierType);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 GrXferProcessor* GrXPFactory::createXferProcessor(const GrProcOptInfo& colorPOI,
                                                   const GrProcOptInfo& coveragePOI,
                                                   const GrDeviceCoordTexture* dstCopy,
                                                   const GrDrawTargetCaps& caps) const {
 #ifdef SK_DEBUG
     if (this->willReadDstColor(caps, colorPOI, coveragePOI)) {
         if (!caps.shaderCaps()->dstReadInShaderSupport()) {
             SkASSERT(dstCopy && dstCopy->texture());
         } else {
             SkASSERT(!dstCopy || !dstCopy->texture()); 
         }
     } else {
         SkASSERT(!dstCopy || !dstCopy->texture()); 
     }
 #endif
     return this->onCreateXferProcessor(caps, colorPOI, coveragePOI, dstCopy);
 }
 
 bool GrXPFactory::willNeedDstCopy(const GrDrawTargetCaps& caps, const GrProcOptInfo& colorPOI,
                                   const GrProcOptInfo& coveragePOI) const {
     return (this->willReadDstColor(caps, colorPOI, coveragePOI) 
             && !caps.shaderCaps()->dstReadInShaderSupport());
 }