Update shelf spacing in Chrome OS according to the MD specs

ash/system/tray/system_tray.h

Index: ash/system/tray/system_tray.h
diff --git a/ash/system/tray/system_tray.h b/ash/system/tray/system_tray.h
index 1e5502a6e778919347eb33963e0b39abcfedd35c..a9eb362d84e9225e05b4ceee4d9323b41957ce7f 100644
--- a/ash/system/tray/system_tray.h
+++ b/ash/system/tray/system_tray.h
@@ -157,6 +157,8 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
   // Gets tray_date_ for browser tests.
   TrayDate* GetTrayDateForTesting() const;
 
+  void GetHitRegionInsets(gfx::Insets& insets) override;
+
  private:
   // Creates the default set of items for the sytem tray.
   void CreateItems(SystemTrayDelegate* delegate);