Add a row in the network tray to inform users to turn Bluetooth on to enable Tether.

ash/system/network/network_list.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/system/network/network_list.h"
 
 #include <memory>
 #include <utility>
 
 #include "ash/metrics/user_metrics_recorder.h"
@@ skipping 638 matching lines @@
     if (info_label) {
       needs_relayout_ = true;
       delete info_label;
       *info_label_ptr = nullptr;
     }
     return;
   }
   if (!info_label)
     info_label = new InfoLabel(message_id);
   else
-    info_label->SetMessage(message_id);
+    info_label->Update(message_id);
   PlaceViewAtIndex(info_label, insertion_index);
   *info_label_ptr = info_label;
 }
 
 int NetworkListView::UpdateSectionHeaderRow(NetworkTypePattern pattern,
                                             bool enabled,
                                             int child_index,
                                             SectionHeaderRowView** view,
                                             views::Separator** separator_view) {
   if (!*view) {
@@ skipping 63 matching lines @@
       TriView::Container::CENTER, views::CreateEmptyBorder(gfx::Insets(
                                       0, 0, 0, kTrayPopupLabelRightPadding)));
 
   // Nothing to the right of the text.
   connection_warning->SetContainerVisible(TriView::Container::END, false);
   return connection_warning;
 }
 
 }  // namespace tray
 }  // namespace ash