Support regular expressions in GitilesPoller branch spec.
Support regular expressions in GitilesPoller branch spec.

New branches that match a given regular expression will be
discovered and polled without a master restart.

R=kmg@chromium.org,nodir@chromium.org

Review URL: https://codereview.chromium.org/421293007

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@286240 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build