T is computed as
   *   sum(contributionToEQT(window, task) * task.weight)
   * for all tasks in weightedTasks, where
   * - contributionToEQT is the function defined above.
   * - task.weight is an arbitrary number between 0.0 and 1.0. This is useful
   *   for computing contribution of chrome subcomponents (e.g. GC) to
   *   the expected queueing time for EQT diagnostics.
   *
   * We assume that input arrival time is uniformly distributed in the given
   * time window.
   *
   * @param {!tr.b.math.Range