Use highp for gpu bezier effects

BUG=skia:2860
R=bsalomon@google.com

Author: egdaniel@google.com

Review URL: https://codereview.chromium.org/519473003
diff --git a/src/gpu/gl/builders/GrGLShaderBuilder.cpp b/src/gpu/gl/builders/GrGLShaderBuilder.cpp
index 4dea142..6b3e1d1 100644
--- a/src/gpu/gl/builders/GrGLShaderBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLShaderBuilder.cpp
@@ -62,6 +62,12 @@
     , fFeaturesAddedMask(0) {
 }
 
+void GrGLShaderBuilder::declAppend(const GrGLShaderVar& var) {
+    SkString tempDecl;
+    var.appendDecl(fProgramBuilder->ctxInfo(), &tempDecl);
+    this->codeAppendf("%s;", tempDecl.c_str());
+}
+
 void GrGLShaderBuilder::emitFunction(GrSLType returnType,
                                      const char* name,
                                      int argCnt,