Use noperspective interpolation for 2D draws

src/gpu/glsl/GrGLSLGeometryProcessor.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLSLGeometryProcessor.h"
 
 #include "GrCoordTransform.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "glsl/GrGLSLProcessorTypes.h"
 #include "glsl/GrGLSLUniformHandler.h"
 #include "glsl/GrGLSLVarying.h"
 #include "glsl/GrGLSLVertexShaderBuilder.h"
 
 void GrGLSLGeometryProcessor::emitCode(EmitArgs& args) {
     GrGLSLVertexBuilder* vBuilder = args.fVertBuilder;
     GrGPArgs gpArgs;
     this->onEmitCode(args, &gpArgs);
     vBuilder->transformToNormalizedDeviceSpace(gpArgs.fPositionVar);
+    if (kVec2f_GrSLType == gpArgs.fPositionVar.getType()) {
+        args.fVaryingHandler->setNoPerspective();
+    }
 }
 
 void GrGLSLGeometryProcessor::emitTransforms(GrGLSLVertexBuilder* vb,
                                              GrGLSLVaryingHandler* varyingHandler,
                                              GrGLSLUniformHandler* uniformHandler,
                                              const GrShaderVar& posVar,
                                              const char* localCoords,
                                              const SkMatrix& localMatrix,
                                              const TransformsIn& tin,
                                              TransformsOut* tout) {
@@ skipping 115 matching lines @@
             gpArgs->fPositionVar.set(kVec2f_GrSLType, "pos2");
             vertBuilder->codeAppendf("vec2 %s = vec2(%s * vec3(%s, 1));",
                                      gpArgs->fPositionVar.c_str(), viewMatrixName, posName);
         } else {
             gpArgs->fPositionVar.set(kVec3f_GrSLType, "pos3");
             vertBuilder->codeAppendf("vec3 %s = %s * vec3(%s, 1);",
                                      gpArgs->fPositionVar.c_str(), viewMatrixName, posName);
         }
     }
 }