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

ash/system/tray/tray_popup_item_style.h

 // 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.
 
 #ifndef ASH_SYSTEM_TRAY_TRAY_POPUP_ITEM_STYLE_H_
 #define ASH_SYSTEM_TRAY_TRAY_POPUP_ITEM_STYLE_H_
 
 #include "base/macros.h"
 #include "third_party/skia/include/core/SkColor.h"
 
@@ skipping 26 matching lines @@
     TITLE,
     // Main text used by default view rows.
     DEFAULT_VIEW_LABEL,
     // Text in sub-section header rows in detailed views.
     SUB_HEADER,
     // Main text used by detailed view rows.
     DETAILED_VIEW_LABEL,
     // System information text (e.g. date/time, battery status, "Scanning for
     // devices..." seen in the Bluetooth detailed view, etc).
     SYSTEM_INFO,
+    // System information text within a clickable row.
+    CLICKABLE_SYSTEM_INFO,
     // Child buttons within rows that have a visible border (e.g. Cast's
     // "Stop", etc).
     BUTTON,
     // Sub text within a row (e.g. user name in user row).
     CAPTION,
   };
 
   static constexpr double kInactiveIconAlpha = 0.54;
 
   static SkColor GetIconColor(ColorStyle color_style);
@@ skipping 20 matching lines @@
   FontStyle font_style_;
 
   ColorStyle color_style_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayPopupItemStyle);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_TRAY_POPUP_ITEM_STYLE_H_