[CastRunner] Don't pass VULKAN context flag in headless tests

It's an error to enable VULKAN without exposing
fuchsia.vulkan.loader.Loader in the sandbox.

The rest of the flags are still ignored and left as a TODO.

Bug: 1059497
Change-Id: I96a4c1f51b5ee76f5df075a53afd92e029169f9a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2093052
Commit-Queue: Michael Spang <spang@chromium.org>
Auto-Submit: Michael Spang <spang@chromium.org>
Reviewed-by: Fabrice de Gans-Riberi <fdegans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747963}

fuchsia/runners/cast/cast_runner.cc

@@ -33,11 +33,23 @@ fuchsia::web::CreateContextParams BuildCreateContextParamsForIsolatedRunners(
   fuchsia::web::CreateContextParams output;
 
   // Isolated contexts receive only a limited set of features.
-  output.set_features(
-      fuchsia::web::ContextFeatureFlags::AUDIO |
-      fuchsia::web::ContextFeatureFlags::VULKAN |
-      fuchsia::web::ContextFeatureFlags::HARDWARE_VIDEO_DECODER |
-      fuchsia::web::ContextFeatureFlags::HARDWARE_VIDEO_DECODER_ONLY);
+  fuchsia::web::ContextFeatureFlags features =
+      fuchsia::web::ContextFeatureFlags::AUDIO;
+
+  if ((create_context_params.features() &
+       fuchsia::web::ContextFeatureFlags::HEADLESS) ==
+      fuchsia::web::ContextFeatureFlags::HEADLESS) {
+    features |= fuchsia::web::ContextFeatureFlags::HEADLESS;
+  } else {
+    features |= fuchsia::web::ContextFeatureFlags::VULKAN |
+                fuchsia::web::ContextFeatureFlags::HARDWARE_VIDEO_DECODER |
+                fuchsia::web::ContextFeatureFlags::HARDWARE_VIDEO_DECODER_ONLY;
+  }
+
+  // The rest of |create_context_params.features()| is ignored.
+  // TODO(crbug.com/1059497): Respect the flags or don't pass them in tests.
+
+  output.set_features(features);
 
   if (create_context_params.has_user_agent_product()) {
     output.set_user_agent_product(create_context_params.user_agent_product());