Use noperspective interpolation for 2D draws

src/gpu/gl/GrGLVaryingHandler.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 "gl/GrGLVaryingHandler.h"
 
 #include "gl/GrGLGpu.h"
 #include "gl/builders/GrGLProgramBuilder.h"
 
 
 GrGLSLVaryingHandler::VaryingHandle GrGLVaryingHandler::addPathProcessingVarying(
                                                                        const char* name,
                                                                        GrGLSLVertToFrag* v,
                                                                        GrSLPrecision fsPrecision) {
 #ifdef SK_DEBUG
     GrGLProgramBuilder* glPB = (GrGLProgramBuilder*) fProgramBuilder;
     // This call is not used for non-NVPR backends.
     SkASSERT(glPB->gpu()->glCaps().shaderCaps()->pathRenderingSupport() &&
              glPB->fArgs.fPrimitiveProcessor->isPathRendering() &&
              !glPB->fArgs.fPrimitiveProcessor->willUseGeoShader() &&
              glPB->fArgs.fPrimitiveProcessor->numAttribs() == 0);
 #endif
     this->addVarying(name, v, fsPrecision);
-    VaryingInfo& varyingInfo = fPathProcVaryingInfos.push_back();
-    varyingInfo.fVariable = fFragInputs.back();
+    auto varyingInfo = fPathProcVaryingInfos.push_back();
     varyingInfo.fLocation = fPathProcVaryingInfos.count() - 1;
     return VaryingHandle(varyingInfo.fLocation);
 }
+
+void GrGLVaryingHandler::onFinalize() {
+    SkASSERT(fPathProcVaryingInfos.empty() || fPathProcVaryingInfos.count() == fFragInputs.count());
+    for (int i = 0; i < fPathProcVaryingInfos.count(); ++i) {
+        fPathProcVaryingInfos[i].fVariable = fFragInputs[i];
+    }
+}