Make spacing between uber tray items consistent with UI spec.

ash/system/power/tray_power.cc

Index: ash/system/power/tray_power.cc
diff --git a/ash/system/power/tray_power.cc b/ash/system/power/tray_power.cc
index 866964d57bbf6b2723b6334b85749651d1c239d3..09ac2d95f09ba7caea1292532ae838d2b2d44219 100644
--- a/ash/system/power/tray_power.cc
+++ b/ash/system/power/tray_power.cc
@@ -198,6 +198,10 @@ void TrayPower::DestroyNotificationView() {
 void TrayPower::UpdateAfterLoginStatusChange(user::LoginStatus status) {
 }
 
+void TrayPower::UpdateAfterShelfAlignmentChange(ShelfAlignment alignment) {
+  SetTrayImageItemBorder(power_tray_, alignment);
+}
+
 void TrayPower::OnPowerStatusChanged(const PowerSupplyStatus& status) {
   if (power_tray_)
     power_tray_->UpdatePowerStatus(status);