Add unit test for vertex attribute count.

src/gpu/GrTest.cpp

Index: src/gpu/GrTest.cpp
diff --git a/src/gpu/GrTest.cpp b/src/gpu/GrTest.cpp
index 4c5ce8e09925b61bade9248aaee52655d2dab6e4..c9b26e284af5bf2d651a42b7d3b056ce71b60404 100644
--- a/src/gpu/GrTest.cpp
+++ b/src/gpu/GrTest.cpp
@@ -188,6 +188,7 @@ void GrGpu::Stats::dumpKeyValuePairs(SkTArray<SkString>* keys, SkTArray<double>*
     keys->push_back(SkString("shader_compilations")); values->push_back(fShaderCompilations);
     keys->push_back(SkString("texture_uploads")); values->push_back(fTextureUploads);
     keys->push_back(SkString("number_of_draws")); values->push_back(fNumDraws);
+    keys->push_back(SkString("number_of_failed_draws")); values->push_back(fNumFailedDraws);
 }
 
 #endif