Make GrPrimitiveProcessor::Attribute a class, hide data members.

Change-Id: I008881d79c82fdde6bb68fe2218e62ccc9c538dd
Reviewed-on: https://skia-review.googlesource.com/130600
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/tests/PrimitiveProcessorTest.cpp b/tests/PrimitiveProcessorTest.cpp
index 3a9ab8d..95855e0 100644
--- a/tests/PrimitiveProcessorTest.cpp
+++ b/tests/PrimitiveProcessorTest.cpp
@@ -73,7 +73,8 @@
                     void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override {
                         const GP& gp = args.fGP.cast<GP>();
                         args.fVaryingHandler->emitAttributes(gp);
-                        this->writeOutputPosition(args.fVertBuilder, gpArgs, gp.getAttrib(0).fName);
+                        this->writeOutputPosition(args.fVertBuilder, gpArgs,
+                                                  gp.getAttrib(0).name());
                         GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
                         fragBuilder->codeAppendf("%s = half4(1);", args.fOutputColor);
                         fragBuilder->codeAppendf("%s = half4(1);", args.fOutputCoverage);