Bug 853998 - Add a common "SyncRunnable" class which dispatches events totally synchronously, avoiding event loop spinning or automatic promotion of this event to a nsThread, r=bsmedberg
Bug 853998 - Convert sync dispatches from SIPCC threads to use SyncRunnable r=jesup
Bug 853998 test (WIP)
Bug 853998 - Test for SyncRunnable r=jesup