[iOS][Alert] Add style for actions

Improves the style of the actions to be like the UX mocks.

Bug: 951358, 951300
Change-Id: I535fd2ba711321d782d1ff0c5bb41781523aef88
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1578745
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653552}
4 files changed