Summary:
Similar to D29786190 (https://github.com/facebook/react-native/commit/b0e39b2ed9b66b378eb75bee9e692fc801431ddd) on iOS, keeps cursor position constant to the end of the text whenever text changes without selection updates.
Changelog: [Internal]
Reviewed By: mdvacca
Differential Revision: D29879663
fbshipit-source-id: da1b50a99ae3b9ef796423146ba49e4172e286df