Don't create parallel request if download is about to complete

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index cbc2af415e46b6e89b2edfe137c5060f9b031328..0ed544d30b22a542a4e620af2977802359684568 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13937,6 +13937,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Download.ParallelDownload.RemainingTimeWhenBuildingRequests"
+    units="seconds">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Records the remaining download time when building parallel requests.
+  </summary>
+</histogram>
+
 <histogram name="Download.ParallelDownloadAddStreamSuccess"
     enum="BooleanSuccess">
   <owner>xingliu@chromium.org</owner>
@@ -106264,6 +106272,8 @@ from previous Chrome versions.
   <int value="4" label="No content length header"/>
   <int value="5" label="File size does not meet the requirement."/>
   <int value="6" label="HTTP connection type mismatch."/>
+  <int value="7"
+      label="Remaining download time does not meet the requirement."/>
 </enum>
 
 <enum name="ParsedCookieStatus" type="int">