This replaces time ruler on top of lower pane of the Timeline panel with frame "bars" that show frame durarion (if fits). The plan is to show additional information on hover over these bars.
Created attachment 135627 [details] Patch
Created attachment 135630 [details] screenshot (bars wide enough for frame duration to fit)
Created attachment 135632 [details] screenshot (small bars, no text)
Committed r113314: <http://trac.webkit.org/changeset/113314>