GitLab

Fixes how //content/test/gpu runs PyLint during presubmit. Previously,
it relied on lint_unittest.py to be picked up when running all the other
tests in //content/test/gpu/gpu_tests, which has the downside of making
PyLint not cover other directories in //content/test/gpu. Instead, we
now use the canned check that pretty much all of Chromium uses.

Also fixes all the PyLint issues that were found as a result of this
switch.

Bug: 1133587
Change-Id: Idd7ce9f5aad3e1d02c8d7dbcbd7eeb131fdff725
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2508952
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Auto-Submit: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822486}