chromeos: Remove TrayBubbleView::Delegate::OnBeforeBubbleWidgetInit

ash/system/tray/tray_background_view.h

Index: ash/system/tray/tray_background_view.h
diff --git a/ash/system/tray/tray_background_view.h b/ash/system/tray/tray_background_view.h
index 08ace17f534a7f71dd776661f8e62301a8555f5c..8a3b1f305649261523a7b1f2990d682b1091cd43 100644
--- a/ash/system/tray/tray_background_view.h
+++ b/ash/system/tray/tray_background_view.h
@@ -99,6 +99,9 @@ class ASH_EXPORT TrayBackgroundView : public ActionableView,
   // tray_container().
   gfx::Insets GetBubbleAnchorInsets() const;
 
+  // Returns the container window for the bubble (on the proper display).
+  aura::Window* GetBubbleWindowContainer() const;
+
  protected:
   // ActionableView:
   std::unique_ptr<views::InkDropMask> CreateInkDropMask() const override;