Improve test failure reporting.

For our video tests we use image comparison to compare several images
captured during a test run with golden images captured ahead of time.

Currently, if such a comparison fails, testers have to go dig out
comparison links in a series of clicks/logs scouring to examine the
failed comparison.

This CL puts comparison links and other comparison test results right on
the failure message so that it is visible in wmatrix for faster
triaging.

BUG=None.
TEST=Ran video_GlitchDetection.mp4.480p tests on link and observed the
report on failure.

Change-Id: I1aa038272b2dff6cd5b9724a6a45d34f18ef096f
Reviewed-on: https://chromium-review.googlesource.com/217163
Reviewed-by: Mussa Kiroga <mussa@chromium.org>
Tested-by: Mussa Kiroga <mussa@chromium.org>
Commit-Queue: Mussa Kiroga <mussa@chromium.org>
5 files changed