[perf] gcssource uses SourceConfig.Subscription.
[perf] gcssource uses SourceConfig.Subscription.

Change-Id: I58360ff8a695d8dada7c8e742fdffa4747e806f6
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/475538
Commit-Queue: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Auto-Submit: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@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