Don't ref/unref the static src-over xp

src/gpu/GrPipeline.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrPipeline_DEFINED
 #define GrPipeline_DEFINED
 
@@ skipping 85 matching lines @@
     // Make the renderTarget's drawTarget (if it exists) be dependent on any
     // drawTargets in this pipeline
     void addDependenciesTo(GrRenderTarget* rt) const;
 
     int numColorFragmentProcessors() const { return fNumColorProcessors; }
     int numCoverageFragmentProcessors() const {
         return fFragmentProcessors.count() - fNumColorProcessors;
     }
     int numFragmentProcessors() const { return fFragmentProcessors.count(); }
 
-    const GrXferProcessor* getXferProcessor() const { return fXferProcessor.get(); }
+    const GrXferProcessor& getXferProcessor() const {
+        if (fXferProcessor.get()) {
+            return *fXferProcessor.get();
+        } else {
+            // A null xp member means the common src-over case. GrXferProcessor's ref'ing
+            // mechanism is not thread safe so we do not hold a ref on this global.
+            return GrPorterDuffXPFactory::SimpleSrcOverXP();
+        }
+    }
 
     const GrFragmentProcessor& getColorFragmentProcessor(int idx) const {
         SkASSERT(idx < this->numColorFragmentProcessors());
         return *fFragmentProcessors[idx].get();
     }
 
     const GrFragmentProcessor& getCoverageFragmentProcessor(int idx) const {
         SkASSERT(idx < this->numCoverageFragmentProcessors());
         return *fFragmentProcessors[fNumColorProcessors + idx].get();
     }
@@ skipping 12 matching lines @@
     GrRenderTarget* getRenderTarget() const { return fRenderTarget.get(); }
 
     const GrStencilSettings& getStencil() const { return fStencilSettings; }
 
     const GrScissorState& getScissorState() const { return fScissorState; }
 
     bool isHWAntialiasState() const { return SkToBool(fFlags & kHWAA_Flag); }
     bool snapVerticesToPixelCenters() const { return SkToBool(fFlags & kSnapVertices_Flag); }
 
     GrXferBarrierType xferBarrierType(const GrCaps& caps) const {
-        return fXferProcessor->xferBarrierType(fRenderTarget.get(), caps);
+        return this->getXferProcessor().xferBarrierType(fRenderTarget.get(), caps);
     }
 
     /**
      * Gets whether the target is drawing clockwise, counterclockwise,
      * or both faces.
      * @return the current draw face(s).
      */
     GrPipelineBuilder::DrawFace getDrawFace() const { return fDrawFace; }
 
 
@@ skipping 42 matching lines @@
     bool                                fReadsFragPosition;
     bool                                fIgnoresCoverage;
 
     // This value is also the index in fFragmentProcessors where coverage processors begin.
     int                                 fNumColorProcessors;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif