Fix Edit() focus on Android.
Fix Edit() focus on Android.

- Give a correct focus to Edit widget on Android().
- Due to SDL issues, there still be some issues on Android.
  1) When switching focus from Edit to Edit, SW keyboard doesn't
     show up for 2nd Edit widget.
     (Tracked by https://bugzilla.libsdl.org/show_bug.cgi?id=3186).
  2) When an app goes to background and become foreground, SW
     keyboard doesn't restore.
     (Tracked by https://bugzilla.libsdl.org/show_bug.cgi?id=3187).

Bug: b/25776016.
Tested: on OSX, Android.
Change-Id: Ib611754dc8354d7d921796332468c68d8c8fd74e

google/flatui,google/flatui,google/flatui,google/flatui