MD system tray: Avoid adding separator as the first item of Bluetooth device list.

ash/common/system/chromeos/bluetooth/tray_bluetooth.cc

Index: ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
diff --git a/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc b/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
index ed5ae69e926e18cd0126486268aa33cde4a3cf58..028be209532d1b5c3da7ea348e76c342e066b4d8 100644
--- a/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
+++ b/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
@@ -331,8 +331,10 @@ class BluetoothDetailedView : public TrayDetailsView {
                                       false, bluetooth_enabled);
     if (discovered_not_paired_devices_.size() > 0) {
       if (UseMd()) {
-        scroll_content()->AddChildView(
-            TrayPopupUtils::CreateListItemSeparator(false));
+        if (scroll_content()->has_children()) {
+          scroll_content()->AddChildView(
+              TrayPopupUtils::CreateListItemSeparator(false));
+        }
       } else {
         AddScrollSeparator();
       }