Disable flaky ChromeVox tests.

These started flaking due to changing timing in the renderer process
during navigation/startup/shutdown.

TBR=dmazzoni@chromium.org

Change-Id: Ic61c7058666612d68b49b8a7f311a957e5bbd647
Bug: 622387
Reviewed-on: https://chromium-review.googlesource.com/c/1361585
Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613661}
1 file changed