Make spacing between uber tray items consistent with UI spec.

ash/system/tray/system_tray_item.h

Index: ash/system/tray/system_tray_item.h
diff --git a/ash/system/tray/system_tray_item.h b/ash/system/tray/system_tray_item.h
index bb1635c20b964d6dc0664832d668def580caddff..afb758dd5dbf0b09a1e9355670269dfffb28c10a 100644
--- a/ash/system/tray/system_tray_item.h
+++ b/ash/system/tray/system_tray_item.h
@@ -17,6 +17,10 @@ class View;
 
 namespace ash {
 
+namespace internal {
+class TrayItemView;
+}
+
 class ASH_EXPORT SystemTrayItem {
  public:
   SystemTrayItem();
@@ -63,6 +67,15 @@ class ASH_EXPORT SystemTrayItem {
   // The default implementation does nothing.
   virtual void UpdateAfterShelfAlignmentChange(ShelfAlignment alignment);
 
+  // Sets the empty border of an image tray item for adjusting the space
+  // around it.
+  virtual void SetTrayImageItemBorder(views::View* tray_view,
+                                      ShelfAlignment alignment);
+  // Sets the empty border around a label tray item for adjusting the space
+  // around it.
+  virtual void SetTrayLabelItemBorder(internal::TrayItemView* tray_view,
+                                      ShelfAlignment alignment);
+
   // Shows the detailed view for this item. If the main popup for the tray is
   // currently visible, then making this call would use the existing window to
   // display the detailed item. The detailed item will inherit the bounds of the