Warn about but ignore multiple attempts to create activity-report histogram.

base/metrics/histogram_base.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 "base/metrics/histogram_base.h"
 
 #include <limits.h>
 
 #include <memory>
 #include <utility>
@@ skipping 107 matching lines @@
   root.SetInteger("flags", flags());
   root.Set("params", std::move(parameters));
   root.Set("buckets", std::move(buckets));
   root.SetInteger("pid", GetUniqueIdForProcess());
   serializer.Serialize(root);
 }
 
 // static
 void HistogramBase::EnableActivityReportHistogram(
     const std::string& process_type) {
-  DCHECK(!report_histogram_);
+  if (report_histogram_)
+    return;
+
   size_t existing = StatisticsRecorder::GetHistogramCount();
   if (existing != 0) {
     DVLOG(1) << existing
              << " histograms were created before reporting was enabled.";
   }
 
   std::string name =
       "UMA.Histograms.Activity" +
       (process_type.empty() ? process_type : "." + process_type);
 
@@ skipping 80 matching lines @@
         report_histogram_->Add(HISTOGRAM_REPORT_FLAG_UMA_TARGETED);
       break;
 
     case HISTOGRAM_LOOKUP:
       report_histogram_->Add(HISTOGRAM_REPORT_HISTOGRAM_LOOKUP);
       break;
   }
 }
 
 }  // namespace base