Remove DCHECK when initializing the TabUsageRecorder.

chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc

 // Copyright (c) 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 "chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 395 matching lines @@
       kStartupMetricsGatheringDelay);
 #endif  // defined(OS_WIN)
 
   display_count_ = display::Screen::GetScreen()->GetNumDisplays();
   UMA_HISTOGRAM_COUNTS_100("Hardware.Display.Count.OnStartup", display_count_);
   display::Screen::GetScreen()->AddObserver(this);
   is_screen_observer_ = true;
 
 #if !defined(OS_ANDROID)
   metrics::BeginFirstWebContentsProfiling();
-  metrics::TabUsageRecorder::Initialize();
+  metrics::TabUsageRecorder::InitializeIfNeeded();
 #endif  // !defined(OS_ANDROID)
 }
 
 void ChromeBrowserMainExtraPartsMetrics::OnDisplayAdded(
     const display::Display& new_display) {
   EmitDisplaysChangedMetric();
 }
 
 void ChromeBrowserMainExtraPartsMetrics::OnDisplayRemoved(
     const display::Display& old_display) {
@@ skipping 12 matching lines @@
   }
 }
 
 namespace chrome {
 
 void AddMetricsExtraParts(ChromeBrowserMainParts* main_parts) {
   main_parts->AddParts(new ChromeBrowserMainExtraPartsMetrics());
 }
 
 }  // namespace chrome