This is a preview UI of data captured by Gecko Backtrack
Each thread has two 'tapes' displaying intervals of various activity. The first tape (above) shows events that had to happen to achieve the selected goal (for this example case it's all between load start and first-paint of my blog main page.) The second tape (bellow) shows events happening in parallel but not related to achieving the goal and potentially blocking the main goal path.
Black and gray blocks are clickable - reveal stack samples. Hovering any color block will show an info tooltip with more details.
Stack samples show class names, method names and call nesting, and also names of resources the running objects work with.
      CPU critical       CPU blocking       idle       I/O       network wait       dispatch       mutex wait       queued