[iOS][Alert] Take into account current safe area

Adds consideration for any overlapping safe area with the keyboard.

R=kkhorimoto@chromium.org

Bug: 959737, 951300
Change-Id: Ie8de14175eb6654cb540684797fe5e79e493127d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1605900
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659886}
1 file changed