Don't reset scroll position of contents on every ScrollView layout.

ash/common/system/tray/tray_details_view.cc

Index: ash/common/system/tray/tray_details_view.cc
diff --git a/ash/common/system/tray/tray_details_view.cc b/ash/common/system/tray/tray_details_view.cc
index d6c6ea55df3c980096237ba8bc17f49042491925..9ba0e8280082e7255b0f6c84f3efa9d8f6670f7a 100644
--- a/ash/common/system/tray/tray_details_view.cc
+++ b/ash/common/system/tray/tray_details_view.cc
@@ -420,9 +420,10 @@ void TrayDetailsView::Layout() {
     views::View::Layout();
     if (scroller_ && !scroller_->is_bounded())
       scroller_->ClipHeightTo(0, scroller_->height());
+    return;
   }
 
-  if (UseMd() || bounds().IsEmpty()) {
+  if (bounds().IsEmpty()) {
     views::View::Layout();
     return;
   }