Validate PublishHandler.ViewerIsOwner with auth.Allowed

Change-Id: Ic12926696a6f082a794577e395ff277bbb34daec
Merge "Validate PublishHandler.ViewerIsOwner with auth.Allowed"
Fix build with Go tip. Will file upstream bug.

Change-Id: I1081ff8498caf809c6b4e22a284a59b95032c3ce