This documentation concerns vr_browser_test.h, vr_browser_test.cc, and files that use them.
These files port the framework used by VR instrumentation tests (located in //chrome/android/javatests/src/org/chromium/chrome/browser/vr/ and documented in //chrome/android/javatests/src/org/chromium/chrome/browser/vr/*.md) for use in browser tests in order to test VR features on desktop platforms.
This is pretty much a direct port, with the same JavaScript/HTML files being used for both and the Java/C++ code being functionally equivalent to each other, so the instrumentation test's documentation on writing tests using the framework is applicable here, too. As such, this documentation covers any notable differences between the two implementations.
Both the instrumentation tests and browser tests have hardware/software restrictions - in the case of browser tests, VR is only supported on Windows 8 and later (or Windows 7 with a non-standard patch applied) with a GPU that supports DirectX 11.1.
Instrumentation tests handle restrictions with the @Restriction annotation, but browser tests don't have any equivalent functionality. Instead, test names should be wrapped in the REQUIRES_GPU macro defined in vr_browser_test.h, which simply disables the test by default. We then explicitly run tests that inherit from VrBrowserTest and enable the running of disabled tests on bots that meet the requirements.
Instrumentation tests are able to add and remove command line switches on a per-test-case basis using @CommandLine annotations, but equivalent functionality does not exist in browser tests.
Instead, if different command line flags are needed, a new class will need to be created that extends VrBrowserTest and overrides the flags that are set in its SetUp function.