Mark more video tests with preload=auto to avoid metadata suspend.

This patch just marks the tests with the preload=auto attribute to avoid
delays in the first frame that these tests were relying on. A later
patch will try enabling preload=metadata lazy load on macOS.

BUG=879406,965983
R=sandersd

Change-Id: I9e64fe1c43d55fdafe76271cd73afb91bc8e2fec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1629209
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663254}
14 files changed