Added Ash.SystemMenu.DefaultView.VisibleItems histogram.

ash/system/chromeos/tray_display.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/chromeos/tray_display.h"
 
 #include <memory>
 #include <utility>
 #include <vector>
 
@@ skipping 300 matching lines @@
     label_->SizeToFit(label_max_width);
   }
 
   views::ImageView* image_;
   views::Label* label_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayView);
 };
 
 TrayDisplay::TrayDisplay(SystemTray* system_tray)
-    : SystemTrayItem(system_tray), default_(NULL) {
+    : SystemTrayItem(system_tray, UMA_DISPLAY), default_(nullptr) {
   WmShell::Get()->AddDisplayObserver(this);
   UpdateDisplayInfo(NULL);
 }
 
 TrayDisplay::~TrayDisplay() {
   WmShell::Get()->RemoveDisplayObserver(this);
 }
 
 void TrayDisplay::UpdateDisplayInfo(TrayDisplay::DisplayInfoMap* old_info) {
   if (old_info)
@@ skipping 140 matching lines @@
 bool TrayDisplay::GetAccessibleStateForTesting(ui::AXViewState* state) {
   views::View* view = default_;
   if (view) {
     view->GetAccessibleState(state);
     return true;
   }
   return false;
 }
 
 }  // namespace ash