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

ash/system/network/network_list.h

Index: ash/system/network/network_list.h
diff --git a/ash/system/network/network_list.h b/ash/system/network/network_list.h
index 7fcd2d448b54ea48462d919d03104e08e44edd5e..a04370c2d92caa742fca3261cb277b384f47c220 100644
--- a/ash/system/network/network_list.h
+++ b/ash/system/network/network_list.h
@@ -32,7 +32,8 @@ namespace tray {
 // A list of available networks of a given type. This class is used for all
 // network types except VPNs. For VPNs, see the |VPNList| class.
 class NetworkListView : public NetworkStateListDetailedView,
-                        public network_icon::AnimationObserver {
+                        public network_icon::AnimationObserver,
+                        public TrayDetailsView::InfoLabelDelegate {
  public:
   class SectionHeaderRowView;
 
@@ -106,6 +107,9 @@ class NetworkListView : public NetworkStateListDetailedView,
                        int insertion_index,
                        InfoLabel** info_label_ptr);
 
+  // InfoLabelDelegate:

[Kyle Horimoto, 2017/07/10 18:37:07]

nit: Overrides should generally go at the bottom of the list of functions in the
.h file.

[lesliewatkins, 2017/07/12 21:49:50]

Done.

+  void OnLabelClicked(InfoLabel* label);

[James Cook, 2017/07/10 18:43:03]

Probably needs "override"

[lesliewatkins, 2017/07/12 21:49:50]

Done.

+
   // Creates a cellular/tether/Wi-Fi header row |view| and adds it to
   // |scroll_content()| if necessary and reorders the |scroll_content()| placing
   // the |view| at |child_index|. Returns the index where the next child should