Merge branch 'stable-3.0' into stable-3.1

* stable-3.0:
  CreateChangesTriggeringGc: Support existing project
  Upgrade bazlets to latest stable-3.0 to build with 3.0.11 API
  Remove the commented-out snapshot plugin api lines

Change-Id: Ia3b459d0cdaffac434244c5344c08f048bc4f9a0