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

ash/system/tray_update.cc

Index: ash/system/tray_update.cc
diff --git a/ash/system/tray_update.cc b/ash/system/tray_update.cc
index 2e0e97dd146424d5c3a1e0e7f5202f87930e3f98..24bece745de8149a31cf7785a92bbd58ecb1094c 100644
--- a/ash/system/tray_update.cc
+++ b/ash/system/tray_update.cc
@@ -99,11 +99,11 @@ namespace tray {
 
 class UpdateNagger : public ui::LayerAnimationObserver {
  public:
-  explicit UpdateNagger(SystemTrayItem* owner)
-      : owner_(owner) {
+  explicit UpdateNagger(SystemTrayItem* tray)
+      : tray_(tray) {
     RestartTimer();
-    Shell::GetInstance()->system_tray()->GetWidget()->GetNativeView()->layer()->
-        GetAnimator()->AddObserver(this);
+    tray_->system_tray()->GetWidget()->GetNativeView()->layer()->GetAnimator()->
+        AddObserver(this);
   }
 
   virtual ~UpdateNagger() {
@@ -125,7 +125,7 @@ class UpdateNagger : public ui::LayerAnimationObserver {
 
  private:
   void Nag() {
-    owner_->PopupDetailedView(kShowUpdateNaggerForSeconds, false);
+    tray_->PopupDetailedView(kShowUpdateNaggerForSeconds, false);
   }
 
   // Overridden from ui::LayerAnimationObserver.
@@ -145,7 +145,7 @@ class UpdateNagger : public ui::LayerAnimationObserver {
   virtual void OnLayerAnimationScheduled(
       ui::LayerAnimationSequence* sequence) OVERRIDE {}
 
-  SystemTrayItem* owner_;
+  SystemTrayItem* tray_;
   base::OneShotTimer<UpdateNagger> timer_;
 
   DISALLOW_COPY_AND_ASSIGN(UpdateNagger);
@@ -153,8 +153,8 @@ class UpdateNagger : public ui::LayerAnimationObserver {
 
 }  // namespace tray
 
-TrayUpdate::TrayUpdate()
-    : TrayImageItem(IDR_AURA_UBER_TRAY_UPDATE),
+TrayUpdate::TrayUpdate(SystemTray* system_tray)
+    : TrayImageItem(system_tray, IDR_AURA_UBER_TRAY_UPDATE),
       severity_(UpdateObserver::UPDATE_NORMAL) {
 }