Add core/timing/ objects to USED_FROM_MULTIPLE_THREADS

After r167398, test_resource_dedicated_worker.html was failing because UserTiming is touched by workers. This CL adds UserTiming and other objects in core/timing/ to USED_FROM_MULTIPLE_THREADS.

BUG=340522
R=tkent@chromium.org

Review URL: https://codereview.chromium.org/172983004

git-svn-id: svn://svn.chromium.org/blink/trunk@167450 bbb929c8-8fbe-4397-9dbb-9b2b20218538