Re-enable fast/frames/location-observe-callback-crash.html

It was disabled when Object.observe itself was disabled, but
now that Object.observe is back on this test should be run.

TBR=rafaelw@chromium.org
BUG=367817

Review URL: https://codereview.chromium.org/261373002

git-svn-id: svn://svn.chromium.org/blink/trunk@173347 bbb929c8-8fbe-4397-9dbb-9b2b20218538