Add contains "polyfill" to domUtils

small change, replace isNodeInRoot() in RootCloseWrapper, with a
elem.contains polyfill. offers better performance than recursively
walking up parentNodes, not that it matters much in the instances we use
it.

src/RootCloseWrapper.js

@@ -4,24 +4,6 @@ import EventListener from './utils/EventListener';
 
 // TODO: Merge this logic with dropdown logic once #526 is done.
 
-/**
- * Checks whether a node is within
- * a root nodes tree
- *
- * @param {DOMElement} node
- * @param {DOMElement} root
- * @returns {boolean}
- */
-function isNodeInRoot(node, root) {
-  while (node) {
-    if (node === root) {
-      return true;
-    }
-    node = node.parentNode;
-  }
-
-  return false;
-}
 
 export default class RootCloseWrapper extends React.Component {
   constructor(props) {
@@ -44,7 +26,7 @@ export default class RootCloseWrapper extends React.Component {
     // If the click originated from within this component, don't do anything.
     // e.srcElement is required for IE8 as e.target is undefined
     let target = e.target || e.srcElement;
-    if (isNodeInRoot(target, React.findDOMNode(this))) {
+    if (domUtils.contains(React.findDOMNode(this), target)) {
       return;
     }
 

src/utils/domUtils.js

@@ -113,7 +113,32 @@ function offsetParentFunc(elem) {
   return offsetParent || docElem;
 }
 
+/**
+ * Cross browser .contains() polyfill
+ * @param  {HTMLElement} elem
+ * @param  {HTMLElement} inner
+ * @return {bool}
+ */
+function contains(elem, inner){
+  function ie8Contains(root, node) {
+    while (node) {
+      if (node === root) {
+        return true;
+      }
+      node = node.parentNode;
+    }
+    return false;
+  }
+
+  return (elem && elem.contains)
+      ? elem.contains(inner)
+      : (elem && elem.compareDocumentPosition)
+          ? elem === inner || !!(elem.compareDocumentPosition(inner) & 16)
+          : ie8Contains(elem, inner);
+}
+
 export default {
+  contains,
   ownerDocument,
   getComputedStyles,
   getOffset,