[gold] Add CORS to tree status endpoint
[gold] Add CORS to tree status endpoint

Change-Id: I9a40484beb4cf3911727b1993af880b7d271fa56
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/233466
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Commit-Queue: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@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