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Move from using Cocoa to using Views. The Cocoa version was was causing
problems with app exit dialogs showing up in the wrong process in
RemoteMacViews. This issue was solved by the views version.

Bug: 898604
Change-Id: I30bd1e543fa98a1503d80b4ad3947f676eb5e0c6
Reviewed-on: https://chromium-review.googlesource.com/c/1298300
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605898}