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 3670e9d20f50d763404c55cd8b62b1dead75b309..09b73b050c95bf0f010485c9925d7cce66b54c77 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13036,6 +13036,25 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Download.BandwidthWithoutParallelStreamsBytesPerSecond"

[Ilya Sherman, 2017/03/15 20:54:43]

Optional/FYI: We typically do not include units in metric names (to keep the
names more scannable), but I see that you're matching a previously used
convention for similar histograms, so it's probably reasonable to keep the
suffix here.

+    units="Bytes/second">

[Ilya Sherman, 2017/03/15 20:54:43]

nit: For the units, we prefer lowercase, i.e. "bytes/second"

[qinmin, 2017/03/15 23:20:11]

Done.

+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    For parallel downloading, average disk bandwidth seen when only 1 stream is
+    actively downloading the content. Other streams may have already finished,
+    or have not been created yet.
+  </summary>
+</histogram>
+
+<histogram name="Download.BandwidthWithParallelStreamsBytesPerSecond"
+    units="Bytes/second">

[Ilya Sherman, 2017/03/15 20:54:43]

Ditto

[qinmin, 2017/03/15 23:20:11]

Done.

+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    For parallel downloading, average disk bandwidth seen when parallel streams
+    are downloading the content.
+  </summary>
+</histogram>
+
 <histogram name="Download.ClearAllSize">
   <obsolete>
     Deprecated 1/2017.
@@ -13598,6 +13617,21 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Time between the start of a download and its completion.</summary>
 </histogram>
 
+<histogram name="Download.TimeSavedWithParallelDownload" units="ms">

[Ilya Sherman, 2017/03/15 20:54:43]

Optional nit: I'd include "Estimated" in this metric name, to emphasize that
it's making some assumptions that might not be entirely accurate/should be taken
with a grain of salt.

[qinmin, 2017/03/15 23:20:11]

Done.

+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Estimated time saved on a download when parallel downloading is enabled. To
+    estimate this, the time spent on a download is classified into two
+    categories. The fist category has only one stream active, while other
+    streams are either finished, not started, or failed. And the second category
+    has multiple streams active. By calculating the average bandwidth during the
+    first category, a rough estimation on the time it will save is obtained by
+    assuming all the bytes downloaded during the second category are downloaded
+    by only one stream. The value could be nagative if using parallel requests
+    is slower than using a single request.
+  </summary>
+</histogram>
+
 <histogram name="Download.TimeToRenameFailureAfterInitialFailure" units="ms">
   <owner>asanka@chromium.org</owner>
   <summary>