Add option to add precision to varyings in shader

src/gpu/gl/builders/GrGLFragmentShaderBuilder.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 "GrGLFragmentShaderBuilder.h"
 #include "GrGLShaderStringBuilder.h"
 #include "GrGLProgramBuilder.h"
@@ skipping 177 matching lines @@
                                "1.0);\n", kCoordName, rtHeightName);
             fSetupFragPosition = true;
         }
         SkASSERT(fProgramBuilder->fUniformHandles.fRTHeightUni.isValid());
         return kCoordName;
     }
 }
 
 void GrGLFragmentShaderBuilder::addVarying(GrSLType type,
                const char* name,
-               const char** fsInName) {
-    fInputs.push_back().set(type, GrGLShaderVar::kVaryingIn_TypeModifier, name);
+               const char** fsInName,
+               GrGLShaderVar::Precision fsPrecision) {
+    fInputs.push_back().set(type, GrGLShaderVar::kVaryingIn_TypeModifier, name, fsPrecision);
     if (fsInName) {
         *fsInName = name;
     }
 }
 
 void GrGLFragmentShaderBuilder::bindProgramLocations(GrGLuint programId) {
     GrGpuGL* gpu = fProgramBuilder->gpu();
     if (fHasCustomColorOutput) {
         GL_CALL(BindFragDataLocation(programId, 0, declared_color_output_name()));
     }
@@ skipping 132 matching lines @@
                                  dual_source_output_name());
         fHasSecondaryOutput = true;
     }
     return dual_source_output_name();
 }
 
 const char* GrGLFragmentShaderBuilder::getColorOutputName() const {
     return fHasCustomColorOutput ? declared_color_output_name() : "gl_FragColor";
 }