handleError_(severity, message, href) {
    // Always show the new error if:
    //   1. there is no error showing currently
    //   2. the new error is more severe than the old one
    if (this.currentErrorSeverity_ == null ||
        severity > this.currentErrorSeverity_) {
      this.errorDisplayLink_.href = href;
      // IE8 and other very old browsers don't have textContent.
      if (this.errorDisplayLink_.textContent === undefined) {
        this.errorDisplayLink_.innerText = message;
      } else {
        this.errorDisplayLink_.textContent = message;
      }
      this.currentErrorSeverity_ = severity;
      if (this.errorDisplayLink_.href) {
        this.errorDisplayLink_.classList.remove('input-disabled');
      } else {
        this.errorDisplayLink_.classList.add('input-disabled');
      }
      document.getElementById('error-display').classList.remove('hidden');
    }
  }
@param {!shaka.util.Error.Severity} severity
@param {string} message
@param {string} href
@private