static getExecutionTimingsByGroup(tasks) {
    /** @type {Map<TaskGroupIds, number>} */
    const result = new Map();

    for (const task of tasks) {
      const originalTime = result.get(task.group.id) || 0;
      result.set(task.group.id, originalTime + task.selfTime);
    }

    return result;
  }
@param {LH.Artifacts.TaskNode[]} tasks
@return {Map<TaskGroupIds, number>}