Summary: When you reload and create a new bridge, one of the things that happens during setup is that the RCTAccessibilityManager fires a notification. The old bridge would receive this notification from the new bridge's RCTAccessibilityManager, which we don't want, especially because the two are running on different shadow queues.
I believe this led to a gnarly crash in NSConcreteTextStorage because RCTMeasure in RCTShadowText.m was getting called for the old RCTText (getting destroyed) from a notification fired from the new shadow queue. The fix is for the UIManager to handle notifications only from its bridge's RCTAccessibilityManager. See #2001 for the kinds of crashes we were seeing.
Closes https://github.com/facebook/react-native/pull/3279
Reviewed By: @svcscm
Differential Revision: D2521652
Pulled By: @nicklockwood
fb-gh-sync-id: a4ffe3ef8304667727e573e2a2e8b716e1d2f3e1