static isSupported() {
    // On Edge, ReadableStream exists, but attempting to construct it results in
    // an error. See https://bit.ly/2zwaFLL
    // So this has to check that ReadableStream is present AND usable.
    if (window.ReadableStream) {
      try {
        new ReadableStream({}); // eslint-disable-line no-new
      } catch (e) {
        return false;
      }
    } else {
      return false;
    }
    // Old fetch implementations hasn't body and ReadableStream implementation
    // See: https://github.com/shaka-project/shaka-player/issues/5088
    if (window.Response) {
      const response = new Response('');
      if (!response.body) {
        return false;
      }
    } else {
      return false;
    }
    return !!(window.fetch && !('polyfill' in window.fetch) &&
      window.AbortController);
  }
Determine if the Fetch API is supported in the browser. Note: this is
deliberately exposed as a method to allow the client app to use the same
logic as Shaka when determining support.
@return {boolean}
@export