chromeos: Remove TrayBubbleView::Delegate::OnBeforeBubbleWidgetInit

ash/system/tray/tray_background_view.cc

Index: ash/system/tray/tray_background_view.cc
diff --git a/ash/system/tray/tray_background_view.cc b/ash/system/tray/tray_background_view.cc
index 4a20f8eefbffd2fd8c5068e298f6f18680f1041d..c16c3351c2fb64bed6035429bdaf1ea796f4e38b 100644
--- a/ash/system/tray/tray_background_view.cc
+++ b/ash/system/tray/tray_background_view.cc
@@ -7,6 +7,7 @@
 #include <algorithm>
 
 #include "ash/ash_constants.h"
+#include "ash/public/cpp/shell_window_ids.h"
 #include "ash/shelf/shelf.h"
 #include "ash/shelf/shelf_constants.h"
 #include "ash/shell.h"
@@ -353,6 +354,12 @@ gfx::Insets TrayBackgroundView::GetBubbleAnchorInsets() const {
   }
 }
 
+aura::Window* TrayBackgroundView::GetBubbleWindowContainer() const {
+  return Shell::GetContainer(
+      tray_container()->GetWidget()->GetNativeWindow()->GetRootWindow(),
+      kShellWindowId_SettingBubbleContainer);
+}
+
 std::unique_ptr<views::InkDropMask> TrayBackgroundView::CreateInkDropMask()
     const {
   return base::MakeUnique<views::RoundRectInkDropMask>(