Reland: Add test for system tray network menu icon for extension-controlled networks

ash/common/system/tray/system_tray.h

Index: ash/common/system/tray/system_tray.h
diff --git a/ash/common/system/tray/system_tray.h b/ash/common/system/tray/system_tray.h
index 0e5ed5b1f915c6f6c2b950c36536d7f91a8192a5..1df9954a666fa10a5a85e57550766d53d10f958c 100644
--- a/ash/common/system/tray/system_tray.h
+++ b/ash/common/system/tray/system_tray.h
@@ -29,6 +29,7 @@ class TrayAccessibility;
 class TrayAudio;
 class TrayCast;
 class TrayDate;
+class TrayNetwork;
 class TraySystemInfo;
 class TrayTiles;
 class TrayUpdate;
@@ -164,6 +165,7 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
 
   TrayCast* GetTrayCastForTesting() const;
   TrayDate* GetTrayDateForTesting() const;
+  TrayNetwork* GetTrayNetworkForTesting() const;
   TraySystemInfo* GetTraySystemInfoForTesting() const;
   TrayTiles* GetTrayTilesForTesting() const;
   TrayUpdate* GetTrayUpdateForTesting() const;
@@ -267,6 +269,7 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
   TrayAudio* tray_audio_;  // May be null.
   TrayCast* tray_cast_;
   TrayDate* tray_date_;    // null for material design.
+  TrayNetwork* tray_network_;
   TrayTiles* tray_tiles_;  // only used in material design.
   TraySystemInfo* tray_system_info_;  // only used in material design.
   TrayUpdate* tray_update_;