tree 018b7755a546f18ee54e3fc48d6f8c69fdbcc67d
parent 5e933847cc9e7826f1a9ee8b3dc1df4960b1ea5d
author Thomas Van Lenten <thomasvl@google.com> 1458573074 -0400
committer Thomas Van Lenten <thomasvl@google.com> 1458573074 -0400

Only create the readonlySemaphore on demand.

This will lower the amount of dispatch_semaphores created per Message when the
full object tree isn't walked in a way that would require them to be created.
Uses a dispatch_once_t for one time init of the dispatch_semaphore.