Fix UnifiedSystemTray animation on lock screen.

UnifiedSystemTray animation in lock screen was broken because
https://crrev.com/c/1156203 did not consider the added view for
calculating GetExpandedHeight().

TEST=manual
BUG=871192

Change-Id: I4704c3f6ee1a4196e852718fc2c094179f834b38
Reviewed-on: https://chromium-review.googlesource.com/1164871Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Commit-Queue: Tetsui Ohkubo <tetsui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581428}

ash/system/unified/unified_system_tray_view.cc

@@ -377,7 +377,10 @@ void UnifiedSystemTrayView::SetExpandedAmount(double expanded_amount) {
 }
 
 int UnifiedSystemTrayView::GetExpandedHeight() const {
-  return top_shortcuts_view_->GetPreferredSize().height() +
+  return (notification_hidden_view_->visible()
+              ? notification_hidden_view_->GetPreferredSize().height()
+              : 0) +
+         top_shortcuts_view_->GetPreferredSize().height() +
          feature_pods_container_->GetExpandedHeight() +
          sliders_container_->GetExpandedHeight() +
          system_info_view_->GetPreferredSize().height();