Add appendPrecisionModifier method to GrGLSLShaderBuilder

src/gpu/glsl/GrGLSL.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLSL_DEFINED
 #define GrGLSL_DEFINED
 
@@ skipping 66 matching lines @@
 }
 
 /**
  * Adds a line of GLSL code to declare the default precision for float types.
  */
 void GrGLSLAppendDefaultFloatPrecisionDeclaration(GrSLPrecision,
                                                   const GrGLSLCaps& glslCaps,
                                                   SkString* out);
 
 /**
+ * Converts a GrSLPrecision to its corresponding GLSL precision qualifier.
+ */
+static inline const char* GrGLSLPrecisionString(GrSLPrecision p) {
+    switch (p) {
+        case kLow_GrSLPrecision:
+            return "lowp";
+        case kMedium_GrSLPrecision:
+            return "mediump";
+        case kHigh_GrSLPrecision:
+            return "highp";
+        default:
+            SkFAIL("Unexpected precision type.");
+            return "";
+    }
+}
+
+/**
  * Converts a GrSLType to a string containing the name of the equivalent GLSL type.
  */
 static inline const char* GrGLSLTypeString(GrSLType t) {
     switch (t) {
         case kVoid_GrSLType:
             return "void";
         case kFloat_GrSLType:
             return "float";
         case kVec2f_GrSLType:
             return "vec2";
@@ skipping 260 matching lines @@
 
 /**
  * Does an inplace mul, *=, of vec4VarName by mulFactor.
  * A semicolon is added after the assignment.
  */
 void GrGLSLMulVarBy4f(SkString* outAppend, const char* vec4VarName, const GrGLSLExpr4& mulFactor);
 
 #include "GrGLSL_impl.h"
 
 #endif