Add new UMA stats for parallelizable download

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 9ea9c3bdd199b9ac8d937e21a2b1ecbf54f70884..bcd95bc0b4811ede1061d13d6d8ef1da665acbc5 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13467,27 +13467,6 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
-<histogram name="Download.BandwidthWithoutParallelStreamsBytesPerSecond"
-    units="bytes/second">
-  <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. If a download was ever paused, this is not
-    recorded.
-  </summary>
-</histogram>
-
-<histogram name="Download.BandwidthWithParallelStreamsBytesPerSecond"
-    units="bytes/second">
-  <owner>qinmin@chromium.org</owner>
-  <summary>
-    For parallel downloading, average disk bandwidth seen when parallel streams
-    are downloading the content. If a download was ever paused, this is not
-    recorded.
-  </summary>
-</histogram>

[Ilya Sherman, 2017/04/19 00:29:41]

Please mark these as <obsolete> rather than deleting their metadata.

[qinmin, 2017/04/19 22:42:33]

Done.

-
 <histogram name="Download.ClearAllSize">
   <obsolete>
     Deprecated 1/2017.
@@ -14007,6 +13986,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram base="true" name="Download.ParallelizableDownloadBandwidth"
+    units="bytes/second">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    For parallelizable download, average disk bandwidth seen for different
+    settings. If a download was ever paused, this is not recorded.
+  </summary>
+</histogram>
+
 <histogram name="Download.PotentialBandwidth" units="Bytes/second">
   <obsolete>
     Deprecated January 2017.
@@ -123078,7 +123066,7 @@ from previous Chrome versions.
 
 <histogram_suffixes name="ParallelDownload" separator=".">
   <suffix name="ParallelDownload"
-      label="Download that supports parallel requests."/>
+      label="Download that uses parallel requests."/>
   <affected-histogram name="Download.Counts"/>
   <affected-histogram name="Download.InterruptedAtEndReason"/>
   <affected-histogram name="Download.InterruptedOverrunBytes"/>
@@ -123088,6 +123076,25 @@ from previous Chrome versions.
   <affected-histogram name="Download.InterruptedUnderrunBytes"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="ParallelizableDownload" separator=".">
+  <suffix name="ParallelizableDownload"
+      label="Download that supports but doesn't use parallel requests."/>
+  <affected-histogram name="Download.ParallelizableDownloadBandwidth"/>
+</histogram_suffixes>

[Ilya Sherman, 2017/04/19 00:29:41]

nit: Please combine this with the histogram_suffixes element below -- or am I
missing something?

[qinmin, 2017/04/19 22:42:33]

Sorry, the affected-histogram name should be Download.Counts, corrected.

+
+<histogram_suffixes name="ParallelizableDownloadBandwidth" separator=".">
+  <suffix name="WithParallelRequestsSingleStream"
+      label="Bandwidth when only a single stream is active while using
+             parallel requests. Other streams are either finished or haven't
+             started."/>
+  <suffix name="WithParallelRequestsMultipleStreams"
+      label="Bandwidth when multiple streams are active while using parallel
+             requests."/>
+  <suffix name="WithoutParallelRequests"
+      label="Bandwidth without using parallel requests."/>

[Ilya Sherman, 2017/04/19 00:29:41]

How does this differ from ParallelizableDownload?

[qinmin, 2017/04/19 22:42:33]

Fixed the affected-histogram for ParallelizableDownload. This is for bandwidth
metrics, the ParallelizableDownload is for Download.counts.

+  <affected-histogram name="Download.ParallelizableDownloadBandwidth"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="PasswordCustomPassphrase" separator=".">
   <suffix name="WithCustomPassphrase"/>
   <suffix name="WithoutCustomPassphrase"/>