context.addHitRegion should return if the DOMException occurs.

It may randomly make a crash or an unknown error.

BUG=387561

Review URL: https://codereview.chromium.org/331803004

git-svn-id: svn://svn.chromium.org/blink/trunk@176795 bbb929c8-8fbe-4397-9dbb-9b2b20218538