Show small notification icons in notification tray (reland)

ash/common/system/tray/tray_background_view.cc

Index: ash/common/system/tray/tray_background_view.cc
diff --git a/ash/common/system/tray/tray_background_view.cc b/ash/common/system/tray/tray_background_view.cc
index 4d209a56ee1e9af7bda33876a4415957c03a3709..e6393764d72dda2bf251ca1f66e52c3359dffb96 100644
--- a/ash/common/system/tray/tray_background_view.cc
+++ b/ash/common/system/tray/tray_background_view.cc
@@ -174,6 +174,11 @@ void TrayBackgroundView::TrayContainer::SetAlignment(ShelfAlignment alignment) {
   UpdateLayout();
 }
 
+void TrayBackgroundView::TrayContainer::SetMargin(const gfx::Insets& margin) {
+  margin_ = margin;
+  UpdateLayout();
+}
+
 gfx::Size TrayBackgroundView::TrayContainer::GetPreferredSize() const {
   if (size_.IsEmpty())
     return views::View::GetPreferredSize();
@@ -206,8 +211,9 @@ void TrayBackgroundView::TrayContainer::UpdateLayout() {
     // Additional padding used to adjust the user-visible size of status tray
     // dark background.
     const int padding = 3;
-    SetBorder(
-        views::Border::CreateEmptyBorder(padding, padding, padding, padding));
+    SetBorder(views::Border::CreateEmptyBorder(gfx::Insets(padding) + margin_));
+  } else {
+    SetBorder(views::Border::CreateEmptyBorder(margin_));
   }
 
   views::BoxLayout* layout = new views::BoxLayout(orientation, 0, 0, 0);