Show small notification icons in notification tray (reland)

ash/common/system/tray/tray_background_view.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_COMMON_SYSTEM_TRAY_TRAY_BACKGROUND_VIEW_H_
 #define ASH_COMMON_SYSTEM_TRAY_TRAY_BACKGROUND_VIEW_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 25 matching lines @@
   // auto-resizes the widget when necessary.
   class TrayContainer : public views::View {
    public:
     explicit TrayContainer(ShelfAlignment alignment);
     ~TrayContainer() override {}
 
     void SetAlignment(ShelfAlignment alignment);
 
     void set_size(const gfx::Size& size) { size_ = size; }
 
+    void SetMargin(const gfx::Insets& margin);
+
     // views::View:
     gfx::Size GetPreferredSize() const override;
 
    protected:
     // views::View:
     void ChildPreferredSizeChanged(views::View* child) override;
     void ChildVisibilityChanged(View* child) override;
     void ViewHierarchyChanged(
         const ViewHierarchyChangedDetails& details) override;
 
    private:
     void UpdateLayout();
 
     ShelfAlignment alignment_;
     gfx::Size size_;
+    gfx::Insets margin_;
 
     DISALLOW_COPY_AND_ASSIGN(TrayContainer);
   };
 
   explicit TrayBackgroundView(WmShelf* wm_shelf);
   ~TrayBackgroundView() override;
 
   // Called after the tray has been added to the widget containing it.
   virtual void Initialize();
 
@@ skipping 98 matching lines @@
 
   std::unique_ptr<TrayWidgetObserver> widget_observer_;
   std::unique_ptr<TrayEventFilter> tray_event_filter_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayBackgroundView);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_TRAY_BACKGROUND_VIEW_H_