rails/rails — pull request #15943 by wagenet (2014-06-27 19:11:07+00:00)
Title: Always instrument ActiveSupport::Cache

The current approach is broken because it uses a thread local value which
means on multi-threaded environments it has to be turned on per thread.
Secondly, ActiveSupport::Notifications does not instrument items when there
are not subscribers so this flag is unnecessary.