[task scheduler] Fix triggering for non-master branches
[task scheduler] Fix triggering for non-master branches

BUG=skia:5924

Change-Id: I7b89b393fc24b0be452b089fec459c3f51ee0eef
Reviewed-on: https://skia-review.googlesource.com/4301
Reviewed-by: Ben Wagner <3ef7217be91069877d94f7907ce5479000772cd3@google.com>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot