Remove DCHECK when initializing the TabUsageRecorder.

chrome/browser/metrics/tab_usage_recorder.cc

Index: chrome/browser/metrics/tab_usage_recorder.cc
diff --git a/chrome/browser/metrics/tab_usage_recorder.cc b/chrome/browser/metrics/tab_usage_recorder.cc
index d8537d80067fa7d7d6c7d986dc5fef49302b2f6d..15b0e16e22d6a77ad3c7e738548ddb3330bca466 100644
--- a/chrome/browser/metrics/tab_usage_recorder.cc
+++ b/chrome/browser/metrics/tab_usage_recorder.cc
@@ -90,9 +90,9 @@ void TabUsageRecorder::WebContentsData::RecordTabReactivation() {
 }
 
 // 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) {