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This to fix application menu Close Window for mac views like
-- save info to restore closed window
-- check onbeforeunload event

Bug: 751018
Change-Id: I7a99def820f066fc1f47c3c2bae3a2abb49106ff
Reviewed-on: https://chromium-review.googlesource.com/591848
Commit-Queue: Boris Yusupov <boriay@yandex-team.ru>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491457}