Don't assert when clicking on a <button> and then switching to a different app.
Don't assert when clicking on a <button> and then switching to a different app.

BUG=364304
TEST=code is less trigger-happy
R=tkent@chromium.org

Review URL: https://codereview.chromium.org/240433003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@171831 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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