Convert some unit tests from NullGL to Mock context

Bug: skia:
Change-Id: I6ecfed3f7ee096f85ea4cb4920e1029227d36169
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/203703
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/tests/GrPorterDuffTest.cpp b/tests/GrPorterDuffTest.cpp
index 0733bde..435459b 100644
--- a/tests/GrPorterDuffTest.cpp
+++ b/tests/GrPorterDuffTest.cpp
@@ -975,16 +975,13 @@
     TEST_ASSERT(blendInfo.fWriteColor);
 }
 
-// The NullGL context does not work correctly if the GL interface/validation
-// logic is disabled.
-#if !SK_DISABLE_GL_INTERFACE
 DEF_GPUTEST(PorterDuffNoDualSourceBlending, reporter, options) {
     GrContextOptions opts = options;
     opts.fSuppressDualSourceBlending = true;
     sk_gpu_test::GrContextFactory mockFactory(opts);
-    GrContext* ctx = mockFactory.get(sk_gpu_test::GrContextFactory::kNullGL_ContextType);
+    GrContext* ctx = mockFactory.get(sk_gpu_test::GrContextFactory::kMock_ContextType);
     if (!ctx) {
-        SK_ABORT("Failed to create null context without ARB_blend_func_extended.");
+        SK_ABORT("Failed to create mock context without ARB_blend_func_extended.");
         return;
     }
 
@@ -992,7 +989,7 @@
     GrProxyProvider* proxyProvider = ctx->priv().proxyProvider();
     const GrCaps& caps = *ctx->priv().caps();
     if (caps.shaderCaps()->dualSourceBlendingSupport()) {
-        SK_ABORT("Null context failed to honor request for no ARB_blend_func_extended.");
+        SK_ABORT("Mock context failed to honor request for no ARB_blend_func_extended.");
         return;
     }
 
@@ -1032,4 +1029,3 @@
     }
     gpu->deleteTestingOnlyBackendTexture(backendTex);
 }
-#endif