Add a new UMA enum to record how many download uses parallel requests

content/browser/download/download_item_impl.cc

Index: content/browser/download/download_item_impl.cc
diff --git a/content/browser/download/download_item_impl.cc b/content/browser/download/download_item_impl.cc
index 2e998f079d0606ba07f3875eac852da15983fd14..507ace3f58836cc192837a19cf459b4915197981 100644
--- a/content/browser/download/download_item_impl.cc
+++ b/content/browser/download/download_item_impl.cc
@@ -1272,6 +1272,9 @@ void DownloadItemImpl::Start(
   if (state_ == RESUMING_INTERNAL)
     UpdateValidatorsOnResumption(new_create_info);
 
+  if (state_ == INITIAL_INTERNAL && job_->UsesParallelRequests())
+    RecordDownloadCount(USES_PARALLEL_REQUESTS);
+
   TransitionTo(TARGET_PENDING_INTERNAL);
 
   job_->Start();