Added Ash.SystemMenu.DefaultView.VisibleItems histogram.

ash/common/system/chromeos/tray_tracing.cc

 // Copyright 2013 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/common/system/chromeos/tray_tracing.h"
 
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/metrics/user_metrics_action.h"
 #include "ash/common/system/tray/actionable_view.h"
 #include "ash/common/system/tray/fixed_sized_image_view.h"
@@ skipping 58 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(DefaultTracingView);
 };
 
 }  // namespace tray
 
 ////////////////////////////////////////////////////////////////////////////////
 // ash::TrayTracing
 
 TrayTracing::TrayTracing(SystemTray* system_tray)
-    : TrayImageItem(system_tray, IDR_AURA_UBER_TRAY_TRACING), default_(NULL) {
+    : TrayImageItem(system_tray, IDR_AURA_UBER_TRAY_TRACING, UMA_TRACING),
+      default_(nullptr) {
   DCHECK(system_tray);
   WmShell::Get()->system_tray_notifier()->AddTracingObserver(this);
 }
 
 TrayTracing::~TrayTracing() {
   WmShell::Get()->system_tray_notifier()->RemoveTracingObserver(this);
 }
 
 void TrayTracing::SetTrayIconVisible(bool visible) {
   if (tray_view())
@@ skipping 19 matching lines @@
   default_ = NULL;
 }
 
 void TrayTracing::DestroyDetailedView() {}
 
 void TrayTracing::OnTracingModeChanged(bool value) {
   SetTrayIconVisible(value);
 }
 
 }  // namespace ash