Using document and window global variables won't cover all cases

[quangbuule]

Hi,
I can see that we are replying to window and document variables, that won't be great for some edge cases.

For example on this instance:
https://github.com/facebook/fbjs/blob/master/src/__forks__/Style.js#L51

var Style = {
  /**
   * Gets the style property for the supplied node. This will return either the
   * computed style, if available, or the declared style.
   *
   * @param {DOMNode} node
   * @param {string} name Style property name.
   * @return {?string} Style property value.
   */
  get: getStyleProperty,

  /**
   * Determines the nearest ancestor of a node that is scrollable.
   *
   * NOTE: This can be expensive if used repeatedly or on a node nested deeply.
   *
   * @param {?DOMNode} node Node from which to start searching.
   * @return {?DOMWindow|DOMElement} Scroll parent of the supplied node.
   */
  getScrollParent: function(node) {
    if (!node) {
      return null;
    }
    while (node && node !== document.body) {
      if (_isNodeScrollable(node, 'overflow') ||
          _isNodeScrollable(node, 'overflowY') ||
          _isNodeScrollable(node, 'overflowX')) {
        return node;
      }
      node = node.parentNode;
    }
    return window;
  },

};

then Style.getScrollParent won't work on the following example:

var iframeEl = document.getElementById('some_iframe');
var scrollParentEl = Style.getScrollParent(iframeEl.contentWindow.document.getElementById('some_element'));

[sophiebits]

Yup. If this is causing a problem in some Facebook project using fbjs, feel free to send a pull request. (If not, we don't have the time to support other uses of fbjs – sorry.)