Ignored --gtest_output argument again.

It looks like this is the direction that will be necessary in order to
allow Telemetry tests with gtest formatted output to upload results to
the flakiness dashboard. A more general fix will be committed once
this is confirmed to be working.

BUG=225939
R=bajones@chromium.org

Review URL: https://codereview.chromium.org/26312003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227315 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227315