Revert of Fix crash when accessing Event::path(). (patchset #4 id:60001 of https://codereview.chromium.org/516843004/)

Reason for revert:
The test crash-on-querying-event-path.html is unacceptably flaky.
http://test-results.appspot.com/dashboards/flakiness_dashboard.html#group=@ToT%20Blink&tests=http%2Ftests%2Fdom%2Fcrash-on-querying-event-path.html&testType=layout-tests


Original issue's description:
> Fix crash when accessing Event::path().
> 
> (A more elaborate account of the details is found in the bug report.)
> 
> BUG=400476
> R=haraken@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181200

TBR=haraken@chromium.org,vogelheim@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=400476

Review URL: https://codereview.chromium.org/532593002

git-svn-id: svn://svn.chromium.org/blink/trunk@181205 bbb929c8-8fbe-4397-9dbb-9b2b20218538