We missed this because Flow wasn't being run properly on Travis but now that it is, it's clear that #7716 introduced a bunch of new Flow failures. Most of these shouldn't be too bad and I like to say "you break it you buy it" so this one is for you @Aweary :)

There were a couple other pre-existing Flow issues that @vjeux is going to fix, so mostly this should just be the TestRenderer issues.

var index = 0;
    for (var name in children) {
      if (children.hasOwnProperty(name)) {
        var child = children[name];
        var selfDebugID = 0;
        if (__DEV__) {
          selfDebugID = getDebugID(this);
        }
        var mountImage = ReactReconciler.mountComponent(
          child,
          transaction,
          this,
          this._hostContainerInfo,
          context,
          selfDebugID
        );
        child._mountIndex = index++;
        mountImages.push(mountImage);
      }
    }
    if (__DEV__) {
      setChildrenForInstrumentation.call(this, children);
    }
    return mountImages;
  },
  /**
   * Replaces any rendered children with a text content string.
   *
   * @param {string} nextContent String of content.
   * @internal