ive.
   *
   * See https://goo.gl/IN68jL for detailed explanation of definition and
   * motivations. This metric was previously known as "Consistently
   * Interactive". To summarize, we look for a 5 second window starting from
   * between |searchBegin| and |searchEnd| such that there is no long task
   * overlapping with that window, and the entire window is network 2-quiet. A
   * long task is defined as a main thread task with wall duration longer than
   * 50ms, and network 2-quiet means the window ne