Add trailing slash to virtual fast/hidpi/static tests for rebaseline.

The Blink rebaseline bot canonicalizes entries representing a directory to
terminate with a path separator in
TestExpectationParser._collect_matching_tests(). However, in
AutoRebaseline.get_test_prefix_list() we check test presence in a test prefix
list (obtained via TestExpectations.get_needs_rebaseline_failures()), and the
test used as the key is non-canonicalized.

A more long term fix is to ensure we canonicalize the test before checking for
presence, but in interim manually specifying the directories needing rebaseline
to include the expected path separator should allow the tests to be rebaselined
properly.

BUG=577300,485650
TBR=oshima

Review URL: https://codereview.chromium.org/1754963003

Cr-Commit-Position: refs/heads/master@{#378905}
1 file changed