Reduce unnecessary download interruptions due to parallel requests

content/browser/download/download_stats.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 "content/browser/download/download_stats.h"
 
 #include "base/macros.h"
 #include "base/metrics/histogram_functions.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
@@ skipping 799 matching lines @@
       RecordBandwidthMetric(
           "Download.ParallelizableDownloadBandwidth."
           "WithoutParallelRequests",
           bandwidth_without_parallel_streams);
     }
   }
 
   if (!uses_parallel_requests)
     return;
 
+  base::TimeDelta time_saved;
   if (bytes_downloaded_with_parallel_streams > 0) {
     RecordBandwidthMetric(
         "Download.ParallelizableDownloadBandwidth."
         "WithParallelRequestsMultipleStreams",
         CalculateBandwidthBytesPerSecond(bytes_downloaded_with_parallel_streams,
                                          time_with_parallel_streams));
+    if (bandwidth_without_parallel_streams > 0) {
+      time_saved = base::TimeDelta::FromMilliseconds(
+                       1000.0 * bytes_downloaded_with_parallel_streams /
+                       bandwidth_without_parallel_streams) -
+                   time_with_parallel_streams;
+    }
   }
 
-  base::TimeDelta time_saved;
-  if (bandwidth_without_parallel_streams > 0) {
-    time_saved = base::TimeDelta::FromMilliseconds(
-                     1000.0 * bytes_downloaded_with_parallel_streams /
-                     bandwidth_without_parallel_streams) -
-                 time_with_parallel_streams;
-  }
   int kMillisecondsPerHour =
       base::checked_cast<int>(base::Time::kMillisecondsPerSecond * 60 * 60);
   if (time_saved >= base::TimeDelta()) {
     UMA_HISTOGRAM_CUSTOM_COUNTS(
         "Download.EstimatedTimeSavedWithParallelDownload",
         time_saved.InMilliseconds(), 0, kMillisecondsPerHour, 50);
   } else {
     UMA_HISTOGRAM_CUSTOM_COUNTS(
         "Download.EstimatedTimeWastedWithParallelDownload",
         -time_saved.InMilliseconds(), 0, kMillisecondsPerHour, 50);
@@ skipping 89 matching lines @@
 }
 
 void RecordDownloadHttpResponseCode(int response_code) {
   UMA_HISTOGRAM_CUSTOM_ENUMERATION(
       "Download.HttpResponseCode",
       net::HttpUtil::MapStatusCodeForHistogram(response_code),
       net::HttpUtil::GetStatusCodesForHistogram());
 }
 
 }  // namespace content