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

ash/system/tray/tray_details_view.h

Index: ash/system/tray/tray_details_view.h
diff --git a/ash/system/tray/tray_details_view.h b/ash/system/tray/tray_details_view.h
index f046fcdcdeec65b9c5ef0b51d7c26a5ff1a25161..bcff2511afcea2c8ad5ea59b2065a330d90c3eb7 100644
--- a/ash/system/tray/tray_details_view.h
+++ b/ash/system/tray/tray_details_view.h
@@ -8,11 +8,13 @@
 #include <memory>
 
 #include "ash/ash_export.h"
+#include "ash/system/tray/actionable_view.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/system/tray/view_click_listener.h"
 #include "base/macros.h"
 #include "base/timer/timer.h"
 #include "ui/views/controls/button/button.h"
+#include "ui/views/controls/button/label_button.h"
 #include "ui/views/view.h"
 
 namespace gfx {
@@ -61,16 +63,43 @@ class ASH_EXPORT TrayDetailsView : public views::View,
   class InfoLabel : public View {
    public:
     explicit InfoLabel(int message_id);
-    ~InfoLabel() override;
+    virtual void SetMessage(int message_id) = 0;
 
-    void SetMessage(int message_id);
+    DISALLOW_COPY_AND_ASSIGN(InfoLabel);

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

This should be private.

[lesliewatkins, 2017/07/09 00:57:48]

Done.

+  };
+
+  class InfoLabelNoAction : public InfoLabel {

[Kyle Horimoto, 2017/07/07 17:34:00]

nit: tanderson@ probably has a better idea about UI component naming, but I
wouldn't add "NoAction" to the name. Instead, I'd just call this InfoLabel and
have the extended view's name include something about how this is actionable
(i.e., a button).

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

I made a suggestion above that could avoid introducing any new
subclasses. If that doesn't work though, consider if you could have
just two classes:

* InfoLabel (extends View, is non-clickable)
* ClickableInfoLabel (extends InfoLabel, is clickable)

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

Acknowledged.

+   public:
+    InfoLabelNoAction(int message_id);
+
+    // InfoLabel:
+    void SetMessage(int message_id) override;
 
    private:
     views::Label* const label_;
 
-    DISALLOW_COPY_AND_ASSIGN(InfoLabel);
+    DISALLOW_COPY_AND_ASSIGN(InfoLabelNoAction);
   };
 
+  class InfoLabelEnableBluetooth : public InfoLabel,

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

Does this even need to be an InfoLabel at all? The only virtual function exposed
by InfoLabel is SetMessage(), but the message for this View is never actually
changed since this class is only used to display one message.

+                                   public views::ButtonListener {

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

By extending ButtonListener instead of ActionableView, you won't get the
clickable row properties for free: material design "ripple" effect upon clicking
the row, a11y role, etc.

+   public:
+    InfoLabelEnableBluetooth(int message_id);
+
+    // ButtonListener:
+    void ButtonPressed(views::Button* sender, const ui::Event& event) override;
+    // InfoLabel:

[Kyle Horimoto, 2017/07/07 17:34:00]

nit: Newline before this.

+    void SetMessage(int message_id) override;
+
+   private:
+    views::LabelButton* const label_button_;
+
+    DISALLOW_COPY_AND_ASSIGN(InfoLabelEnableBluetooth);
+  };
+
+  // InfoLabel: Factory method

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

nit: Remove this comment and/or change the description to say what it does and
when it should be used.

+  InfoLabel* CreateInfoLabel(int message_id);

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

This should be static.

+
   // views::View:
   void Layout() override;
   int GetHeightForWidth(int width) const override;