Add a delay to send the parallel requests.

content/browser/download/parallel_download_utils.cc

Index: content/browser/download/parallel_download_utils.cc
diff --git a/content/browser/download/parallel_download_utils.cc b/content/browser/download/parallel_download_utils.cc
index 5bd4413c9628aaa6cb4e5ed3f6428919ae1613fd..d4ce68163b5dadad1265b1dffa403222f4ee0cfe 100644
--- a/content/browser/download/parallel_download_utils.cc
+++ b/content/browser/download/parallel_download_utils.cc
@@ -6,6 +6,7 @@
 
 #include "base/metrics/field_trial_params.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/time/time.h"
 #include "content/public/browser/download_save_info.h"
 #include "content/public/common/content_features.h"
 
@@ -28,6 +29,14 @@ const char kParallelRequestCountFinchKey[] = "request_count";
 // specified.
 const int kParallelRequestCount = 2;
 
+// Finch parameter key value for the delay time in milliseconds to send
+// parallel requests after response of the original request is handled.
+const char kParallelRequestDelayFinchKey[] = "parallel_request_delay";
+
+// Default value for parallel request delay.
+const base::TimeDelta kParallelRequestDelay =

[qinmin, 2017/03/15 05:49:18]

move this inside GetParallelRequestDelayConfig(),

[xingliu, 2017/03/15 17:48:52]

Done.

+    base::TimeDelta::FromMilliseconds(0);
+
 // TODO(qinmin): replace this with a comparator operator in
 // DownloadItem::ReceivedSlice.
 bool compareReceivedSlices(const DownloadItem::ReceivedSlice& lhs,
@@ -104,4 +113,13 @@ int GetParallelRequestCountConfig() {
              : kParallelRequestCount;
 }
 
+base::TimeDelta GetParallelRequestDelayConfig() {
+  std::string finch_value = base::GetFieldTrialParamValueByFeature(
+      features::kParallelDownloading, kParallelRequestDelayFinchKey);
+  int64_t time_ms = 0;
+  return !finch_value.empty() && base::StringToInt64(finch_value, &time_ms)

[David Trainor- moved to gerrit, 2017/03/15 03:47:38]

base::StringToInt64 will return false if you pass an empty string.

[xingliu, 2017/03/15 17:48:52]

Done, oh, i see, removed !finch_value.empty().

+             ? base::TimeDelta::FromMilliseconds(time_ms)
+             : kParallelRequestDelay;
+}
+
 }  // namespace content