Summary:
Enable double tap R on iOS, consistent with Android.
Keep the existing Cmd+R on iOS because people are already used to it.
Make Cmd+Key and Double Key both invalid when focus is in textview or textfield.
Also try to add Cmd+R in Android, but seems no good.
Reviewed By: nicklockwood
Differential Revision: D3343907
fbshipit-source-id: 68f7e3b0393711c137e1d932db33e1b6a2a19e09