added support for PLS path rendering

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 "GrPipeline.h"
 #include "GrPipelineBuilder.h"
@@ skipping 199 matching lines @@
 #endif
     return this->onCreateXferProcessor(caps, optimizations, hasMixedSamples, dstTexture);
 }
 
 bool GrXPFactory::willNeedDstTexture(const GrCaps& caps,
                                      const GrPipelineOptimizations& optimizations,
                                      bool hasMixedSamples) const {
     return (this->willReadDstColor(caps, optimizations, hasMixedSamples) &&
             !caps.shaderCaps()->dstReadInShaderSupport());
 }
+
+bool GrXPFactory::willReadDstColor(const GrCaps& caps,
+                                   const GrPipelineOptimizations& optimizations,
+                                   bool hasMixedSamples) const {
+    return optimizations.fOverrides.fUsePLSDstRead || this->onWillReadDstColor(caps, optimizations,
+                                                                               hasMixedSamples);
+}