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

base/metrics/histogram_base.cc

Index: base/metrics/histogram_base.cc
diff --git a/base/metrics/histogram_base.cc b/base/metrics/histogram_base.cc
index 750f0481aabf6bb9825ce0e21483cc8d55038989..671cad24290980512c8d284875915b8443e6deb9 100644
--- a/base/metrics/histogram_base.cc
+++ b/base/metrics/histogram_base.cc
@@ -125,7 +125,9 @@ void HistogramBase::WriteJSON(std::string* output) const {
 // 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