Revert the temporary changes intended for detecting flaky tests.

1. Remove the DCHECKs for swap chain present or commit failures.
   (part of Gerrit review: 1507280)

2. Restore the wait time to 30 frames in Video Path Trace Tests and Video Pixel
Tests.
   (part of Gerrit review: 1500787)

Bug:937545

Change-Id: Id53f222281651a88bb753c126b687f9521abb2e3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1512175
Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Maggie Chen <magchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639088}
2 files changed