Bug 520729 - last loaded title attribute retained during private browsing; r=gavin

browser/base/content/browser.js

@@ -2606,7 +2606,7 @@ function getMarkupDocumentViewer()
  *       browser.js with functionality that can be encapsulated into
  *       browser widget. TEMPORARY!
  *
- * NOTE: Any changes to this routine need to be mirrored in ChromeListener::FindTitleText()
+ * NOTE: Any changes to this routine need to be mirrored in DefaultTooltipTextProvider::GetNodeText()
  *       (located in mozilla/embedding/browser/webBrowser/nsDocShellTreeOwner.cpp)
  *       which performs the same function, but for embedded clients that
  *       don't use a XUL/JS layer. It is important that the logic of
@@ -2616,7 +2616,9 @@ function getMarkupDocumentViewer()
 function FillInHTMLTooltip(tipElement)
 {
   var retVal = false;
-  if (tipElement.namespaceURI == "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul")
+  // Don't show the tooltip if the tooltip node is a XUL element or a document.
+  if (tipElement.namespaceURI == "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" ||
+      !tipElement.ownerDocument)
     return retVal;
 
   const XLinkNS = "http://www.w3.org/1999/xlink";