static async compute_(trace, context) {
    const {mainThreadEvents, frames, timestamps} = await ProcessedTrace.request(trace, context);
    return MainThreadTasks_.getMainThreadTasks(mainThreadEvents, frames, timestamps.traceEnd,
        timestamps.timeOrigin);
  }
@param {LH.Trace} trace
@param {LH.Artifacts.ComputedContext} context
@return {Promise<Array<LH.Artifacts.TaskNode>>}