If JavaScript shows a dialog, cause the page to lose fullscreen.

BUG=670135, 550017, 726761, 728276
TBR=avi@chromium.org

(cherry picked from commit 0720b02e4f303ea6b114d4ae9453e3a7ff55f8dc)

Review-Url: https://codereview.chromium.org/2906133004
Cr-Original-Commit-Position: refs/heads/master@{#478884}
Change-Id: Id833bfcc88e7faf9129ceb3184e11d37a71c61cc
Reviewed-on: https://chromium-review.googlesource.com/576402
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/branch-heads/3112@{#644}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
6 files changed