Make existing unit tests only run on GL contexts

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1869503002

Review URL: https://codereview.chromium.org/1869503002
diff --git a/tests/PrimitiveProcessorTest.cpp b/tests/PrimitiveProcessorTest.cpp
index d25a33c..f8c19e3 100644
--- a/tests/PrimitiveProcessorTest.cpp
+++ b/tests/PrimitiveProcessorTest.cpp
@@ -101,7 +101,7 @@
 };
 }
 
-DEF_GPUTEST_FOR_ALL_CONTEXTS(VertexAttributeCount, reporter, ctxInfo) {
+DEF_GPUTEST_FOR_ALL_GL_CONTEXTS(VertexAttributeCount, reporter, ctxInfo) {
     GrContext* context = ctxInfo.fGrContext;
     GrTextureDesc desc;
     desc.fHeight = 1;