Add option to add precision to varyings in shader

src/gpu/gl/builders/GrGLProgramBuilder.cpp

Index: src/gpu/gl/builders/GrGLProgramBuilder.cpp
diff --git a/src/gpu/gl/builders/GrGLProgramBuilder.cpp b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
index 41b84d806ab3a1b075e675acfd853f27eb2e3a2a..141442d599e5a977a60e14e0574b9b83a41318f2 100644
--- a/src/gpu/gl/builders/GrGLProgramBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
@@ -343,7 +343,8 @@ void GrGLFullProgramBuilder::emitCodeAfterEffects() {
 void GrGLFullProgramBuilder::addVarying(GrSLType type,
                                         const char* name,
                                         const char** vsOutName,
-                                        const char** fsInName) {
+                                        const char** fsInName,
+                                        GrGLShaderVar::Precision fsPrecision) {
     fVS.addVarying(type, name, vsOutName);
 
     SkString* fsInputName = fVS.fOutputs.back().accessName();
@@ -355,7 +356,7 @@ void GrGLFullProgramBuilder::addVarying(GrSLType type,
        fsInputName = fGS.fOutputs.back().accessName();
     }
 #endif
-    fFS.addVarying(type, fsInputName->c_str(), fsInName);
+    fFS.addVarying(type, fsInputName->c_str(), fsInName, fsPrecision);
 }
 
 GrGLFullProgramBuilder::VaryingHandle