Mangle output var in GrGLFragmentProcessor::emitChild

src/effects/SkArithmeticMode_gpu.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 "SkArithmeticMode_gpu.h"
 
 #if SK_SUPPORT_GPU
@@ skipping 42 matching lines @@
 }
 
 class GLArithmeticFP : public GrGLFragmentProcessor {
 public:
     GLArithmeticFP(const GrProcessor&) : fEnforcePMColor(true) {}
 
     ~GLArithmeticFP() override {}
 
     void emitCode(EmitArgs& args) override {
         GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
-        fsBuilder->codeAppend("vec4 _dstColor;");
-        this->emitChild(0, nullptr, "_dstColor", args);
+        SkString dstColor("dstColor");
+        this->emitChild(0, nullptr, &dstColor, args);
 
         fKUni = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                           kVec4f_GrSLType, kDefault_GrSLPrecision,
                                           "k");
         const char* kUni = args.fBuilder->getUniformCStr(fKUni);
 
-        add_arithmetic_code(fsBuilder, args.fInputColor, "_dstColor", args.fOutputColor, kUni,
+        add_arithmetic_code(fsBuilder, args.fInputColor, dstColor.c_str(), args.fOutputColor, kUni,
                             fEnforcePMColor);
     }
 
     static void GenKey(const GrProcessor& proc, const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) {
         const GrArithmeticFP& arith = proc.cast<GrArithmeticFP>();
         uint32_t key = arith.enforcePMColor() ? 1 : 0;
         b->add32(key);
     }
 
 protected:
@@ skipping 209 matching lines @@
     float k1 = d->fRandom->nextF();
     float k2 = d->fRandom->nextF();
     float k3 = d->fRandom->nextF();
     float k4 = d->fRandom->nextF();
     bool enforcePMColor = d->fRandom->nextBool();
 
     return GrArithmeticXPFactory::Create(k1, k2, k3, k4, enforcePMColor);
 }
 
 #endif