Bug 732052 - Internal touch event listeners should not enable slow path. r=smaug

content/events/src/nsEventListenerManager.cpp

@@ -282,7 +282,9 @@ nsEventListenerManager::AddEventListener(nsIDOMEventListener *aListener,
               aTypeAtom == nsGkAtoms::ontouchcancel)) {
     mMayHaveTouchEventListener = true;
     nsPIDOMWindow* window = GetInnerWindowForTarget();
-    if (window)
+    // we don't want touchevent listeners added by scrollbars to flip this flag
+    // so we ignore listeners created with system event flag
+    if (window && !(aFlags & NS_EVENT_FLAG_SYSTEM_EVENT))
       window->SetHasTouchEventListeners();
   } else if (aTypeAtom == nsGkAtoms::onmouseenter ||
              aTypeAtom == nsGkAtoms::onmouseleave) {