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

ash/system/tray/system_tray_unittest.cc

 // Copyright (c) 2012 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.
 
 #include "ash/system/tray/system_tray.h"
 
 #include <vector>
 
 #include "ash/root_window_controller.h"
 #include "ash/system/status_area_widget.h"
@@ skipping 11 matching lines @@
 namespace {
 
 SystemTray* GetSystemTray() {
   return Shell::GetPrimaryRootWindowController()->status_area_widget()->
       system_tray();
 }
 
 // Trivial item implementation that tracks its views for testing.
 class TestItem : public SystemTrayItem {
  public:
-  TestItem() : tray_view_(NULL) {}
+  TestItem() : SystemTrayItem(GetSystemTray()), tray_view_(NULL) {}
 
   virtual views::View* CreateTrayView(user::LoginStatus status) {
     tray_view_ = new views::View;
     // Add a label so it has non-zero width.
     tray_view_->SetLayoutManager(new views::FillLayout);
     tray_view_->AddChildView(new views::Label(UTF8ToUTF16("Tray")));
     return tray_view_;
   }
 
   virtual views::View* CreateDefaultView(user::LoginStatus status) {
@@ skipping 186 matching lines @@
   tray->ShowDefaultView(BUBBLE_USE_EXISTING);
   RunAllPendingInMessageLoop();
 
   EXPECT_EQ(bubble_bounds.ToString(), test_item->default_view()->GetWidget()->
       GetWindowBoundsInScreen().ToString());
   EXPECT_EQ(widget, test_item->default_view()->GetWidget());
 }
 
 }  // namespace test
 }  // namespace ash