Isolate VertexBuilder from GrGLShaderBuilder

src/effects/gradients/SkTwoPointRadialGradient.cpp

Index: src/effects/gradients/SkTwoPointRadialGradient.cpp
diff --git a/src/effects/gradients/SkTwoPointRadialGradient.cpp b/src/effects/gradients/SkTwoPointRadialGradient.cpp
index a3f82ec0389f74eb97b9217840f83b668ff775d8..1a95d6c7b1772d16a8df98ef66bd6edb06782ca2 100644
--- a/src/effects/gradients/SkTwoPointRadialGradient.cpp
+++ b/src/effects/gradients/SkTwoPointRadialGradient.cpp
@@ -548,8 +548,11 @@ void GrGLRadial2Gradient::emitCode(GrGLShaderBuilder* builder,
 
     // For radial gradients without perspective we can pass the linear
     // part of the quadratic as a varying.
-    if (kVec2f_GrSLType == coordsVaryingType) {
-        builder->addVarying(kFloat_GrSLType, "Radial2BCoeff", &fVSVaryingName, &fFSVaryingName);
+    GrGLShaderBuilder::VertexBuilder* radial2BBuilder =
+        (kVec2f_GrSLType == coordsVaryingType) ? builder->getVertexBuilder() : NULL;
+    if (radial2BBuilder) {
+        radial2BBuilder->addVarying(kFloat_GrSLType, "Radial2BCoeff",
+                                    &fVSVaryingName, &fFSVaryingName);
     }
 
     // VS
@@ -561,11 +564,11 @@ void GrGLRadial2Gradient::emitCode(GrGLShaderBuilder* builder,
 
         // For radial gradients without perspective we can pass the linear
         // part of the quadratic as a varying.
-        if (kVec2f_GrSLType == coordsVaryingType) {
+        if (radial2BBuilder) {
             // r2Var = 2 * (r2Parm[2] * varCoord.x - r2Param[3])
-            builder->vsCodeAppendf("\t%s = 2.0 *(%s * %s.x - %s);\n",
-                                   fVSVaryingName, p2.c_str(),
-                                   vsCoordsVarying.c_str(), p3.c_str());
+            radial2BBuilder->vsCodeAppendf("\t%s = 2.0 *(%s * %s.x - %s);\n",
+                                           fVSVaryingName, p2.c_str(),
+                                           vsCoordsVarying.c_str(), p3.c_str());
         }
     }
 
@@ -591,7 +594,7 @@ void GrGLRadial2Gradient::emitCode(GrGLShaderBuilder* builder,
         // If we we're able to interpolate the linear component,
         // bVar is the varying; otherwise compute it
         SkString bVar;
-        if (kVec2f_GrSLType == coordsVaryingType) {
+        if (radial2BBuilder) {
             bVar = fFSVaryingName;
         } else {
             bVar = "b";