ash:Shelf Update Alternate Layout

ash/system/tray/tray_constants.cc

Index: ash/system/tray/tray_constants.cc
diff --git a/ash/system/tray/tray_constants.cc b/ash/system/tray/tray_constants.cc
index 45047e7d5816e74666a4949bdb671f794901bd1c..6d108c8d029877b860046a5471bc70cbf89b509e 100644
--- a/ash/system/tray/tray_constants.cc
+++ b/ash/system/tray/tray_constants.cc
@@ -4,6 +4,7 @@
 
 #include "ash/system/tray/tray_constants.h"
 
+#include "ash/ash_switches.h"
 #include "third_party/skia/include/core/SkColor.h"
 
 namespace ash {
@@ -65,5 +66,13 @@ const int kTrayNotificationContentsWidth = kTrayPopupMinWidth -
     (kNotificationIconWidth + kNotificationButtonWidth +
      (kTrayPopupPaddingHorizontal / 2) * 3);
 const int kTraySpacing = 8;
+const int kAlternateTraySpacing = 4;
+
+// Returns kTraySpacing or kAlternateTraySpacing as applicable
+// (Determined by ash::switches::UseAlternateShelfLayout).
+int GetTraySpacing() {
+  return ash::switches::UseAlternateShelfLayout() ?
+      kAlternateTraySpacing : kTraySpacing;
+}
 
 }  // namespace ash