Skip Video_Context_Loss tests in the trace_test suite.

These were primarily intended to be run as pixel tests. The trace_test
suite seems more stressful and we don't have the resources to
investigate the context loss issues here.

Bug: 974077
Change-Id: Ia6bb6a028e73459bae1ac8cd8de2188235b84a28
Tbr: ynovikov@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1659605
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669109}