--- a/editor/libeditor/nsHTMLEditorEventListener.cpp
+++ b/editor/libeditor/nsHTMLEditorEventListener.cpp
@@ -67,16 +67,21 @@ nsHTMLEditorEventListener::MouseUp(nsIDO
 
   return nsEditorEventListener::MouseUp(aMouseEvent);
 }
 
 nsresult
 nsHTMLEditorEventListener::MouseDown(nsIDOMMouseEvent* aMouseEvent)
 {
   nsHTMLEditor* htmlEditor = GetHTMLEditor();
+  // Contenteditable should disregard mousedowns outside it.
+  // IsAcceptableInputEvent() checks it for a mouse event.
+  if (!htmlEditor->IsAcceptableInputEvent(aMouseEvent)) {
+    return NS_OK;
+  }
 
   // Detect only "context menu" click
   // XXX This should be easier to do!
   // But eDOMEvents_contextmenu and NS_CONTEXTMENU is not exposed in any event
   // interface :-(
   int16_t buttonNumber;
   nsresult rv = aMouseEvent->GetButton(&buttonNumber);
   NS_ENSURE_SUCCESS(rv, rv);
@@ -88,21 +93,16 @@ nsHTMLEditorEventListener::MouseDown(nsI
   NS_ENSURE_SUCCESS(rv, rv);
 
   nsCOMPtr<nsIDOMEventTarget> target;
   rv = aMouseEvent->GetExplicitOriginalTarget(getter_AddRefs(target));
   NS_ENSURE_SUCCESS(rv, rv);
   NS_ENSURE_TRUE(target, NS_ERROR_NULL_POINTER);
   nsCOMPtr<nsIDOMElement> element = do_QueryInterface(target);
 
-  // Contenteditable should disregard mousedowns outside it
-  if (element && !htmlEditor->IsDescendantOfEditorRoot(element)) {
-    return NS_OK;
-  }
-
   if (isContextClick || (buttonNumber == 0 && clickCount == 2)) {
     nsCOMPtr<nsISelection> selection;
     mEditor->GetSelection(getter_AddRefs(selection));
     NS_ENSURE_TRUE(selection, NS_OK);
 
     // Get location of mouse within target node
     nsCOMPtr<nsIDOMNode> parent;
     rv = aMouseEvent->GetRangeParent(getter_AddRefs(parent));