Stop using shell::GetInstance()->system_tray() in system tray items

ash/system/chromeos/network/network_detailed_view.h

Index: ash/system/chromeos/network/network_detailed_view.h
diff --git a/ash/system/chromeos/network/network_detailed_view.h b/ash/system/chromeos/network/network_detailed_view.h
index f0755d78ca013c5ddc8244974de3547054f941ee..3d8a45eec98821f98c31a6b165c536bf73bfa64f 100644
--- a/ash/system/chromeos/network/network_detailed_view.h
+++ b/ash/system/chromeos/network/network_detailed_view.h
@@ -8,6 +8,9 @@
 #include "ash/system/tray/tray_details_view.h"
 
 namespace ash {
+
+class SystemTrayItem;
+
 namespace internal {
 
 namespace tray {
@@ -16,6 +19,8 @@ namespace tray {
 // which includes NetworkWifiDetailedView and NetworkListDetailedViewBase.
 class NetworkDetailedView : public TrayDetailsView {
  public:
+  explicit NetworkDetailedView(SystemTrayItem* tray) : TrayDetailsView(tray) {}
+
   enum DetailedViewType {
     LIST_VIEW,
     WIFI_VIEW,