RequirementsCheckerBrowserTest.Check3DExtension tests the ChromeRequirementsChecker's GPU check, which is done with a content::GpuFeatureChecker::CheckGpuFeatureAvailability call.

The test doesn't actually allow the GPU check to complete (on platforms that support it; I've tested this on my local Linux box).

As a result, the ChromeRequirementsChecker doesn't complete its check, and the test function ValidateRequirementErrors doesn't get called. So the test doesn't check that the RequirementsChecker doesn't eventually fail.

I've tried debugging this and adding threads and message loops, but it dives into some GPU code and I'm not very familiar with how our test threads compare with real threads with respect to GPU queries, so it hasn't been very fruitful.

https://cs.chromium.org/chromium/src/chrome/browser/extensions/requirements_checker_browsertest.cc?type=cs&q=requirements_checker_browsertest&sq=package:chromium&l=160-163

Patch that checks whether the check finishes, causing the test to fail: https://codereview.chromium.org/2776263004/