mash: Convert WebNotificationTray to wm common types

ui/message_center/views/desktop_popup_alignment_delegate.cc

Index: ui/message_center/views/desktop_popup_alignment_delegate.cc
diff --git a/ui/message_center/views/desktop_popup_alignment_delegate.cc b/ui/message_center/views/desktop_popup_alignment_delegate.cc
index f67200def64ace65e3e331bb51c73008d401fac8..27a2aed77f8d0f5e46bb5c7d91da8f0764a2bb0a 100644
--- a/ui/message_center/views/desktop_popup_alignment_delegate.cc
+++ b/ui/message_center/views/desktop_popup_alignment_delegate.cc
@@ -83,6 +83,12 @@ void DesktopPopupAlignmentDelegate::RecomputeAlignment(
       : POPUP_ALIGNMENT_RIGHT;
 }
 
+void DesktopPopupAlignmentDelegate::ConfigureWidgetInitParamsForContainer(
+    views::Widget* widget,
+    views::Widget::InitParams* init_params) {
+  // Do nothing, which will use the default container.
+}
+
 void DesktopPopupAlignmentDelegate::OnDisplayAdded(
     const display::Display& new_display) {}