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.

prevChildren,
    nextNestedChildrenElements,
    mountImages,
    removedNodes,
    transaction,
    context
  ) {
    var nextChildren;
    var selfDebugID = 0;
    if (__DEV__) {
      selfDebugID = getDebugID(this);
      if (this._currentElement) {
        try {
          ReactCurrentOwner.current = this._currentElement._owner;
          nextChildren = flattenChildren(nextNestedChildrenElements, selfDebugID);
        } finally {
          ReactCurrentOwner.current = null;
        }
        ReactChildReconciler.updateChildren(
          prevChildren,
          nextChildren,
          mountImages,
          removedNodes,
          transaction,
          this,
          this._hostContainerInfo,
          context,
          selfDebugID
        );
        return nextChildren;