GTTF: add an option to pass test filter using a file

This is useful when --gtest_filter on the command line would exceed
command line length limits.

This will be used with chromium_trybot recipe to pass a list of tests
to retry after deapplying the patch.

BUG=236893, 44497
R=sky@chromium.org

Review URL: https://codereview.chromium.org/117113003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241833 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241833