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

ash/system/network/network_list.cc

Index: ash/system/network/network_list.cc
diff --git a/ash/system/network/network_list.cc b/ash/system/network/network_list.cc
index 9ed47151bdadd73493461f693f89e7b1972e9aa5..074cb18c73763996bcf228d51b9091d5649d605c 100644
--- a/ash/system/network/network_list.cc
+++ b/ash/system/network/network_list.cc
@@ -641,9 +641,11 @@ void NetworkListView::UpdateInfoLabel(int message_id,
     return;
   }
   if (!info_label)
-    info_label = new InfoLabel(message_id);
+    info_label = TrayDetailsView::CreateInfoLabel(

[Kyle Horimoto, 2017/07/07 17:33:59]

This will only create an info label of a given type once, meaning that if
|message_id| ever changes and requires a different label type, it will never get
updated.

You'll need to check to see if a different label type should be created instead
of just updating the existing one.

[tdanderson, 2017/07/07 21:25:11]

+1, and IMO this is the most awkward part to deal with. Here is another idea I
just had, which may or may not work:

* Don't introduce any new subclasses of InfoLabel.

* Make InfoLabel extend ActionableView (like in your previous patch set).

* Introduce a helper function in network_list.cc (you can put it in an anonymous
namespace of the .cc, doesn't need to be part of the class) called something
like bool IsMessageClickable(int message_id). Based on the message id you pass
in it would return true if that would correspond to a clickable or non-clickable
message.

* Inside UpdateInfoLabel(), you can call
info_label->SetEnabled(IsMessageClickable(message_id)). SetEnabled() is
a method on views::View - if a view is set as disabled that means
it cannot be the target of any events, and thus will not show
the "ripple" effect when clicked even though it is an ActionableView.

* You will also probably want to have an info_label->Update() method
or something that will toggle the font styling based on if it is
clickable or not (clickable should be blue, non-clickable should be
whatever color InfoLabel uses right now). Perhaps also change the
accessibility role to "button" when clickable and "label" when not
clickable.

* You should still not make mention of networking/bluetooth/etc within
the InfoLabel class itself. InfoLabel::PerformAction() could delegate
back to NetworkListView in the following way:

    - Introduce a pure virtual interface InfoLabelDelegate.
      It would have one method, OnLabelClicked(int message_id).
    - Make NetworkListView implement InfoLabelDelegate.
    - Give the InfoLabel class an InfoLabelDelegate member.
    - InfoLabel::PerformAction() would just call
      delegate_->OnLabelClicked(message_id).
    - Then NetworkListView::OnLabelClicked() would perform the
      corresponding action (e.g., launching Bluetooth settings).
      It would probably be a good idea to have
      DCHECK(IsMessageClickable(message_id)) here too.

[Kyle Horimoto, 2017/07/07 21:39:25]

This plan sounds great to me! Leslie, let me know if you need any help
implementing it.

[lesliewatkins, 2017/07/09 00:57:47]

I hopefully did some variation of this, but again, might require fine-tuning.

+        message_id);  // new InfoLabel(message_id);

[Kyle Horimoto, 2017/07/07 17:33:59]

Remove comment, make into a single line of code.

Also, remove the extra line you added below.

[lesliewatkins, 2017/07/09 00:57:47]

Done.

   else
     info_label->SetMessage(message_id);
+
   PlaceViewAtIndex(info_label, insertion_index);
   *info_label_ptr = info_label;
 }