Bug 319659 XPFE code assumes document.firstChild is the root element

p=me r=neil.parkwaycc.co.uk sr=jag

suite/common/contentAreaDD.js

@@ -60,7 +60,7 @@ var contentAreaDNDObserver = {
           /^\s*(javascript|data):/.test(url))
         return;
 
-      switch (document.firstChild.getAttribute('windowtype')) {
+      switch (document.documentElement.getAttribute('windowtype')) {
         case "navigator:browser":
           // Perform a security check before loading the URI
           nsDragAndDrop.dragDropSecurityCheck(aEvent, aDragSession, url);

suite/common/contentAreaUtils.js

@@ -96,7 +96,7 @@ function openNewWindowWith(url, sendReferrer)
   // set, then extract the current charset menu setting from the current document and use it to
   // initialize the new browser window...
   var charsetArg = null;
-  var wintype = document.firstChild.getAttribute('windowtype');
+  var wintype = document.documentElement.getAttribute('windowtype');
   if (wintype == "navigator:browser")
     charsetArg = "charset=" + window.content.document.characterSet;
 
@@ -165,7 +165,7 @@ function openNewTabWith(url, sendReferrer, reverseBackgroundPref)
 
   // As in openNewWindowWith(), we want to pass the charset of the
   // current document over to a new tab.
-  var wintype = browserDocument.firstChild.getAttribute('windowtype');
+  var wintype = browserDocument.documentElement.getAttribute('windowtype');
   var originCharset;
   if (wintype == "navigator:browser") {
     originCharset = window.content.document.characterSet;