Distinguish actions registered with setTimeout() and setInterval().

This change makes actions created with setTimeout() and setInterval()
distinguishable, so actions created with setTimeout() cannot be removed by
clearInterval() (and vice versa).

BUG=230705
R=kbr@chromium.org,haraken@chromium.org

Review URL: https://chromiumcodereview.appspot.com/19494002

git-svn-id: svn://svn.chromium.org/blink/trunk@154624 bbb929c8-8fbe-4397-9dbb-9b2b20218538