Fix GLubyte to GrGLubyte.

BUG=skia:
R=mtklein@google.com

Author: jcgregorio@google.com

Review URL: https://codereview.chromium.org/405433008
diff --git a/bench/nanobench.cpp b/bench/nanobench.cpp
index 5cd3e2f..0af0552 100644
--- a/bench/nanobench.cpp
+++ b/bench/nanobench.cpp
@@ -283,7 +283,7 @@
 
 #if SK_SUPPORT_GPU
 static void fill_gpu_options(ResultsWriter* log, SkGLContextHelper* ctx) {
-    const GLubyte* version;
+    const GrGLubyte* version;
     SK_GL_RET(*ctx, version, GetString(GR_GL_VERSION));
     log->configOption("GL_VERSION", (const char*)(version));