[About] Provide default cancel for overlays

For overlays that do not need to do special things when a
window is dismissed, provide a default cancel function.
This simplifies implementation of the information-only
dialogs, such as the About dialog, WTD-667.

platform/commonUI/dialog/src/DialogService.js

@@ -76,8 +76,8 @@ define(
                     // Add the overlay using the OverlayService, which
                     // will handle actual insertion into the DOM
                     overlay = overlayService.createOverlay(
-                        overlayModel,
-                        "overlay-dialog"
+                        "overlay-dialog",
+                        overlayModel
                     );
 
                     // Track that a dialog is already visible, to