Use noperspective interpolation for 2D draws

src/gpu/glsl/GrGLSLShaderBuilder.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLSLShaderBuilder_DEFINED
 #define GrGLSLShaderBuilder_DEFINED
 
@@ skipping 104 matching lines @@
             fBuilder->codeAppend("}");
         }
     private:
         GrGLSLShaderBuilder* fBuilder;
     };
 
 protected:
     typedef GrTAllocator<GrGLSLShaderVar> VarArray;
     void appendDecls(const VarArray& vars, SkString* out) const;
 
+    /**
+     * Features that should only be enabled internally by the builders.
+     */
+    enum GLSLPrivateFeature {
+        kFragCoordConventions_GLSLPrivateFeature,
+        kBlendEquationAdvanced_GLSLPrivateFeature,
+        kBlendFuncExtended_GLSLPrivateFeature,
+        kExternalTexture_GLSLPrivateFeature,
+        kFramebufferFetch_GLSLPrivateFeature,
+        kNoPerspectiveInterpolation_GLSLPrivateFeature,
+        kLastGLSLPrivateFeature = kNoPerspectiveInterpolation_GLSLPrivateFeature
+    };
+
     /*
      * A general function which enables an extension in a shader if the feature bit is not present
      */
     void addFeature(uint32_t featureBit, const char* extensionName);
 
     enum InterfaceQualifier {
         kOut_InterfaceQualifier,
         kLastInterfaceQualifier = kOut_InterfaceQualifier
     };
 
@@ skipping 51 matching lines @@
 
     VarArray fInputs;
     VarArray fOutputs;
     uint32_t fFeaturesAddedMask;
     SkSTArray<1, SkString> fLayoutParams[kLastInterfaceQualifier + 1];
     int fCodeIndex;
     bool fFinalized;
 
     friend class GrGLSLProgramBuilder;
     friend class GrGLProgramBuilder;
+    friend class GrGLSLVaryingHandler; // to access noperspective interpolation feature.
     friend class GrGLPathProgramBuilder; // to access fInputs.
     friend class GrVkProgramBuilder;
 };
 #endif