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.

);
};
/**
 * Return a function that produces ReactElements of a given type.
 * See https://facebook.github.io/react/docs/top-level-api.html#react.createfactory
 */
ReactElement.createFactory = function(type) {
  var factory = ReactElement.createElement.bind(null, type);
  
  
  
  
  
  factory.type = type;
  return factory;
};
ReactElement.cloneAndReplaceKey = function(oldElement, newKey) {
  var newElement = ReactElement(
    oldElement.type,
    newKey,
    oldElement.ref,
    oldElement._self,
    oldElement._source,
    oldElement._owner,
    oldElement.props
  );
  return newElement;
};
/**
 * Clone and return a new ReactElement using element as the starting point.