The logic added in https://bugs.webkit.org/show_bug.cgi?id=54312 is broken for the case of repeating timers, i.e., those set via setInterval() rather than setTimeout(). The error occurs when the minimum interval is decreased and the timer's repeat interval has already been clamped to the larger value. The current code fails to decrease the repeat interval, leaving the timer running at the slower rate.
Created attachment 83433 [details]
Committed r79455: <http://trac.webkit.org/changeset/79455>