Currently video_VDAPerf is failing on all devices. We can test VDA perf using a fake renderer. Add a new VideoDecodeAccelerator::Client class that does cadence and doesn't actually render. This will require a refactor of video_decode_accelerator_unittest.cc. Another possibility is to modify GLRenderingVDAClient and add yet another parameter. This is not preferred because GLRenderingVDAClient is way too huge.