There is a bug in the logic for determining if `props` is a plain object. This bug results in a false positive, flooding the console with hundreds of instances of this warning: "Expected props argument to be a plain object. Properties defined in its prototype chain will be ignored.".

The code that's failing is in [ReactElement.js, Line 210 in the v15.3.1 branch](https://github.com/facebook/react/blob/v15.3.1/src/isomorphic/classic/element/ReactElement.js#L210) (line number is probably different in master)

> config.**proto** == null || config.**proto** === Object.prototype,

This fails when the props object is created in one iframe, but uses an instance of React from another frame. Each browser window/tab/frame has it's own instance of the Object constructor. For instance, `document.querySelector('iframe').contentWindow.Object === Object` always results in `false`.

Check out this [demo](https://jsfiddle.net/05ugxo5f/4/), which shows the false-positive warning message.

* @param {*} source An annotation object (added by a transpiler or otherwise)
 * indicating filename, line number, and/or other information.
 * @param {*} owner
 * @param {*} props
 * @internal
 */
var ReactElement = function(type, key, ref, self, source, owner, props) {
  var element = {
    
    $$typeof: REACT_ELEMENT_TYPE,
    
    type: type,
    key: key,
    ref: ref,
    props: props,
    
    _owner: owner,
  };
  if (__DEV__) {
    
    
    
    
    element._store = {};
    
    
    
    
    if (canDefineProperty) {
      Object.defineProperty(element._store, 'validated', {