diff -r 000000000000 -r 6474c204b198 layout/xul/nsContainerBoxObject.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/xul/nsContainerBoxObject.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,92 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsCOMPtr.h"
+#include "nsIContainerBoxObject.h"
+#include "nsIBrowserBoxObject.h"
+#include "nsIEditorBoxObject.h"
+#include "nsIIFrameBoxObject.h"
+#include "nsBoxObject.h"
+#include "nsIDocShell.h"
+#include "nsIContent.h"
+#include "nsIDocument.h"
+#include "nsIFrame.h"
+#include "nsSubDocumentFrame.h"
+
+/**
+ * nsContainerBoxObject implements deprecated nsIBrowserBoxObject,
+ * nsIEditorBoxObject and nsIIFrameBoxObject interfaces only because of the
+ * backward compatibility.
+ */
+
+class nsContainerBoxObject : public nsBoxObject,
+                             public nsIBrowserBoxObject,
+                             public nsIEditorBoxObject,
+                             public nsIIFrameBoxObject
+{
+public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSICONTAINERBOXOBJECT
+  NS_DECL_NSIBROWSERBOXOBJECT
+  NS_DECL_NSIEDITORBOXOBJECT
+  NS_DECL_NSIIFRAMEBOXOBJECT
+};
+
+NS_INTERFACE_MAP_BEGIN(nsContainerBoxObject)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsIContainerBoxObject, nsIBrowserBoxObject)
+  NS_INTERFACE_MAP_ENTRY(nsIBrowserBoxObject)
+  NS_INTERFACE_MAP_ENTRY(nsIEditorBoxObject)
+  NS_INTERFACE_MAP_ENTRY(nsIIFrameBoxObject)
+NS_INTERFACE_MAP_END_INHERITING(nsBoxObject)
+
+NS_IMPL_ADDREF_INHERITED(nsContainerBoxObject, nsBoxObject)
+NS_IMPL_RELEASE_INHERITED(nsContainerBoxObject, nsBoxObject)
+
+NS_IMETHODIMP nsContainerBoxObject::GetDocShell(nsIDocShell** aResult)
+{
+  *aResult = nullptr;
+
+  nsSubDocumentFrame *subDocFrame = do_QueryFrame(GetFrame(false));
+  if (subDocFrame) {
+    // Ok, the frame for mContent is an nsSubDocumentFrame, it knows how
+    // to reach the docshell, so ask it...
+
+    return subDocFrame->GetDocShell(aResult);
+  }
+
+  if (!mContent) {
+    return NS_OK;
+  }
+  
+  // No nsSubDocumentFrame available for mContent, try if there's a mapping
+  // between mContent's document to mContent's subdocument.
+
+  // XXXbz sXBL/XBL2 issue -- ownerDocument or currentDocument?
+  nsIDocument *doc = mContent->GetDocument();
+
+  if (!doc) {
+    return NS_OK;
+  }
+  
+  nsIDocument *sub_doc = doc->GetSubDocumentFor(mContent);
+
+  if (!sub_doc) {
+    return NS_OK;
+  }
+
+  NS_IF_ADDREF(*aResult = sub_doc->GetDocShell());
+  return NS_OK;
+}
+
+nsresult
+NS_NewContainerBoxObject(nsIBoxObject** aResult)
+{
+  *aResult = new nsContainerBoxObject();
+  if (!*aResult)
+    return NS_ERROR_OUT_OF_MEMORY;
+  NS_ADDREF(*aResult);
+  return NS_OK;
+}
+