diff --git a/content/events/src/nsDOMDataTransfer.cpp b/content/events/src/nsDOMDataTransfer.cpp
index 8303692b998c..f7a0c793e97d 100644
--- a/content/events/src/nsDOMDataTransfer.cpp
+++ b/content/events/src/nsDOMDataTransfer.cpp
@@ -386,6 +386,24 @@ nsDOMDataTransfer::SetMozCursor(const nsAString& aCursorState)
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDOMDataTransfer::GetMozSourceNode(nsIDOMNode** aSourceNode)
+{
+  *aSourceNode = nsnull;
+
+  nsCOMPtr<nsIDragSession> dragSession = nsContentUtils::GetDragSession();
+  if (!dragSession)
+    return NS_OK;
+
+  nsCOMPtr<nsIDOMNode> sourceNode;
+  dragSession->GetSourceNode(getter_AddRefs(sourceNode));
+  if (sourceNode && !nsContentUtils::CanCallerAccess(sourceNode))
+    return NS_OK;
+
+  sourceNode.swap(*aSourceNode);
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDOMDataTransfer::MozTypesAt(PRUint32 aIndex, nsIDOMDOMStringList** aTypes)
 {
@@ -789,13 +807,7 @@ nsDOMDataTransfer::CacheExternalFormats()
   // asked for, as it may be time consuming for the source application to
   // generate it.
 
-  nsCOMPtr<nsIDragService> dragService =
-    do_GetService("@mozilla.org/widget/dragservice;1");
-  if (!dragService)
-    return;
-
-  nsCOMPtr<nsIDragSession> dragSession;
-  dragService->GetCurrentSession(getter_AddRefs(dragSession));
+  nsCOMPtr<nsIDragSession> dragSession = nsContentUtils::GetDragSession();
   if (!dragSession)
     return;
 
@@ -853,13 +865,7 @@ nsDOMDataTransfer::FillInExternalDragData(TransferItem& aItem, PRUint32 aIndex)
     else if (strcmp(format, "text/uri-list") == 0)
       format = kURLDataMime;
 
-    nsCOMPtr<nsIDragService> dragService =
-      do_GetService("@mozilla.org/widget/dragservice;1");
-    if (!dragService)
-      return;
-
-    nsCOMPtr<nsIDragSession> dragSession;
-    dragService->GetCurrentSession(getter_AddRefs(dragSession));
+    nsCOMPtr<nsIDragSession> dragSession = nsContentUtils::GetDragSession();
     if (!dragSession)
       return;
 
diff --git a/dom/interfaces/events/nsIDOMDataTransfer.idl b/dom/interfaces/events/nsIDOMDataTransfer.idl
index 5b27e0dfb3e6..71e1e264fea7 100644
--- a/dom/interfaces/events/nsIDOMDataTransfer.idl
+++ b/dom/interfaces/events/nsIDOMDataTransfer.idl
@@ -162,7 +162,7 @@ interface nsIDOMDataTransfer : nsISupports
   void addElement(in nsIDOMElement element);
 };
 
-[scriptable, uuid(990758e9-fd38-4444-a1e8-395195802bda)]
+[scriptable, uuid(AE6DF4E2-FA37-4701-A33E-A5678F826EED)]
 interface nsIDOMNSDataTransfer : nsISupports
 {
   /*
@@ -266,4 +266,10 @@ interface nsIDOMNSDataTransfer : nsISupports
    * This property is only relevant for the dragend event.
    */
   readonly attribute boolean mozUserCancelled;
+
+  /**
+   * The node that the mouse was pressed over to begin the drag. For external
+   * drags, or if the caller cannot access this node, this will be null.
+   */
+  readonly attribute nsIDOMNode mozSourceNode;
 };