Add option to add precision to varyings in shader

src/gpu/gl/builders/GrGLProgramBuilder.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 GrGLProgramBuilder_DEFINED
 #define GrGLProgramBuilder_DEFINED
 
@@ skipping 262 matching lines @@
 class GrGLFullProgramBuilder : public GrGLProgramBuilder {
 public:
     GrGLFullProgramBuilder(GrGpuGL*, const GrGLProgramDesc&);
 
    /** Add a varying variable to the current program to pass values between vertex and fragment
         shaders. If the last two parameters are non-NULL, they are filled in with the name
         generated. */
     void addVarying(GrSLType type,
                     const char* name,
                     const char** vsOutName = NULL,
-                    const char** fsInName = NULL);
+                    const char** fsInName = NULL,
+                    GrGLShaderVar::Precision fsPrecision=GrGLShaderVar::kDefault_Precision);
 
     /** Add a separable varying input variable to the current program.
      * A separable varying (fragment shader input) is a varying that can be used also when vertex
      * shaders are not used. With a vertex shader, the operation is same as with other
      * varyings. Without a vertex shader, such as with NV_path_rendering, GL APIs are used to
      * populate the variable. The APIs can refer to the variable through the returned handle.
      */
     VaryingHandle addSeparableVarying(GrSLType type,
                                       const char* name,
                                       const char** vsOutName,
@@ skipping 37 matching lines @@
                                                      int effectCnt,
                                                      const GrGLProgramDesc::EffectKeyProvider&,
                                                      GrGLSLExpr4* inOutFSColor) SK_OVERRIDE;
 
     virtual void emitCodeAfterEffects() SK_OVERRIDE {}
 
     typedef GrGLProgramBuilder INHERITED;
 };
 
 #endif