_handleResize() {
      const documentWidth = document.body.offsetWidth;
      const toPhoneMode = documentWidth <= PHONE_MODE_BREAKPOINT;
      const modeChange = toPhoneMode && !this._phoneMode || !toPhoneMode && this._phoneMode; // XOR not allowed by lint
      if (modeChange) {
        this._phoneMode = toPhoneMode;
      }
    }
Handles document resize to switch between <code>phoneMode</code> and normal appearance.