Clean cherry-pick: [aw] Fix crash when "misbehave" app exits fullscreen.

BUG:17295749

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[aw] Fix crash when "misbehave" app exits fullscreen.

exitFullScreen() might be call without a prior call to
enterFullScreen() if a "misbehave" app overrides onShowCustomView
but does not add the custom view to the window. This fixes a
crash by returning early from exitFullScreen in that case.

BUG=408133

Review URL: https://codereview.chromium.org/501093007

Change-Id: I297f84c42b4cb27d703c43b0e459003ea3425fc2
Cr-Commit-Position: refs/heads/master@{#292165}
1 file changed