This avoids a flickering of the window at the start of every test. Reland with a speculative fix for ViewportTest BUG=angleproject:1105 Change-Id: I83e89881de5b6f58cfb3e14cbe324fd9547f2836 Tested-by: Corentin Wallez <cwallez@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/288533Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>
