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

ash/system/monitor/tray_monitor.cc

Index: ash/system/monitor/tray_monitor.cc
diff --git a/ash/system/monitor/tray_monitor.cc b/ash/system/monitor/tray_monitor.cc
index 4e4336d61591dcc825ad61080d6bd3ce44aa7fac..0d65a46f533279b3907200da1ce26d8857940716 100644
--- a/ash/system/monitor/tray_monitor.cc
+++ b/ash/system/monitor/tray_monitor.cc
@@ -20,7 +20,9 @@ const int kRefreshTimeoutMs = 1000;
 namespace ash {
 namespace internal {
 
-TrayMonitor::TrayMonitor() : label_(NULL) {
+TrayMonitor::TrayMonitor(SystemTray* system_tray)
+    : SystemTrayItem(system_tray),
+      label_(NULL) {
   refresh_timer_.Start(FROM_HERE,
       base::TimeDelta::FromMilliseconds(kRefreshTimeoutMs),
       this, &TrayMonitor::RefreshStats);
@@ -31,7 +33,7 @@ TrayMonitor::~TrayMonitor() {
 }
 
 views::View* TrayMonitor::CreateTrayView(user::LoginStatus status) {
-  TrayItemView* view = new TrayItemView;
+  TrayItemView* view = new TrayItemView(this);
   view->CreateLabel();
   label_ = view->label();
   SetupLabelForTray(label_);