GitLab

Make use of the new polling capabilities of V4L2Device brought by
V4L2DevicePoller to simplify the code.

Bug: 1003223
Test: vdatests passing on Kevin.

Change-Id: Ie44d7d57f5661840f94004f36ac42dae3ebe992f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1799653
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: Chih-Yu Huang <akahuang@chromium.org>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700124}