Make spacing between uber tray items consistent with UI spec.

ash/system/tray/tray_item_view.cc

Index: ash/system/tray/tray_item_view.cc
diff --git a/ash/system/tray/tray_item_view.cc b/ash/system/tray/tray_item_view.cc
index 052d91d7dbdc494e57e16f3c4282e60beb88559f..6bfc0736a5f568115813c25a10e59646bd5d79c0 100644
--- a/ash/system/tray/tray_item_view.cc
+++ b/ash/system/tray/tray_item_view.cc
@@ -11,7 +11,7 @@
 #include "ui/compositor/layer.h"
 #include "ui/views/controls/image_view.h"
 #include "ui/views/controls/label.h"
-#include "ui/views/layout/fill_layout.h"
+#include "ui/views/layout/box_layout.h"
 #include "ui/views/widget/widget.h"
 
 namespace {
@@ -28,7 +28,8 @@ TrayItemView::TrayItemView()
       image_view_(NULL) {
   SetPaintToLayer(true);
   SetFillsBoundsOpaquely(false);
-  SetLayoutManager(new views::FillLayout);
+  SetLayoutManager(
+      new views::BoxLayout(views::BoxLayout::kHorizontal, 0, 0, 0));
 }
 
 TrayItemView::~TrayItemView() {}