Remove DCHECK when initializing the TabUsageRecorder.

chrome/browser/metrics/tab_usage_recorder.cc

 // Copyright 2016 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/tab_usage_recorder.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "content/public/browser/web_contents_user_data.h"
@@ skipping 72 matching lines @@
         "Tab.TimeToReactivation.Important", time_to_reactivation,
         base::TimeDelta::FromSeconds(1), base::TimeDelta::FromHours(2), 100);
   } else {
     UMA_HISTOGRAM_CUSTOM_TIMES(
         "Tab.TimeToReactivation.Normal", time_to_reactivation,
         base::TimeDelta::FromSeconds(1), base::TimeDelta::FromHours(2), 100);
   }
 }
 
 // static
-void TabUsageRecorder::Initialize() {
-  DCHECK(!g_tab_usage_recorder);
-  g_tab_usage_recorder = new TabUsageRecorder();
+void TabUsageRecorder::InitializeIfNeeded() {
+  if (!g_tab_usage_recorder)
+    g_tab_usage_recorder = new TabUsageRecorder();
 }
 
 void TabUsageRecorder::OnTabDeactivated(content::WebContents* contents) {
   GetWebContentsData(contents)->RecordTabDeactivation();
 }
 
 void TabUsageRecorder::OnTabReactivated(content::WebContents* contents) {
   GetWebContentsData(contents)->RecordTabReactivation();
 }
 
@@ skipping 20 matching lines @@
 
 TabUsageRecorder::~TabUsageRecorder() = default;
 
 TabUsageRecorder::WebContentsData* TabUsageRecorder::GetWebContentsData(
     content::WebContents* contents) {
   WebContentsData::CreateForWebContents(contents);
   return WebContentsData::FromWebContents(contents);
 }
 
 }  // namespace metrics