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

content/browser/download/download_stats.h

 // 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.
 //
 // Holds helpers for gathering UMA stats about downloads.
 
 #ifndef CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_STATS_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_STATS_H_
 
 #include <stddef.h>
@@ skipping 73 matching lines @@
 
   // Count of downloads that didn't have a valid WebContents at the time it was
   // interrupted.
   INTERRUPTED_WITHOUT_WEBCONTENTS,
 
   // Count of downloads that supplies a strong validator (implying byte-wise
   // equivalence) and has a 'Accept-Ranges: bytes' header. These downloads are
   // candidates for partial resumption.
   STRONG_VALIDATOR_AND_ACCEPTS_RANGES,
 
+  // Count of downloads that uses parallel download requests.
+  USES_PARALLEL_REQUESTS,
+
   DOWNLOAD_COUNT_TYPES_LAST_ENTRY
 };
 
 enum DownloadSource {
   // The download was initiated when the SavePackage system rejected
   // a Save Page As ... by returning false from
   // SavePackage::IsSaveableContents().
   INITIATED_BY_SAVE_PACKAGE_ON_NON_HTML = 0,
 
   // The download was initiated by a drag and drop from a drag-and-drop
@@ skipping 147 matching lines @@
 
 void RecordDownloadConnectionSecurity(const GURL& download_url,
                                       const std::vector<GURL>& url_chain);
 
 void RecordDownloadSourcePageTransitionType(
     const base::Optional<ui::PageTransition>& transition);
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_STATS_H_