Summary:
A crash encountered in react-native-macOS is very similar to one fixed by https://github.com/microsoft/react-native-macos/pull/489#discussion_r451789471 (see discussion), and it's possible this `replacement` string also suffers from sharing the same backing store as the attributed string (maybe only when the range encompasses the entire string?) and therefore should be copied as well.
Changelog:
[iOS][Fixed] - Possible fix for convertIdToFollyDynamic crash in RCTBaseTextInputView and RCTEventDispatcher
Reviewed By: sammy-SC
Differential Revision: D38064551
fbshipit-source-id: 9c15f2a980155ab3cbb3fde79fcb93b24ee2091a