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 5c644c89bdedc7494b375c9e31d5ee583f8da387..c97fac002c2cb876cc3e349512c1aab819766bde 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13489,6 +13489,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Download.BandwidthWithoutParallelStreamsBytesPerSecond"
     units="bytes/second">
+  <obsolete>
+    Deprecated April 2017.
+  </obsolete>
   <owner>qinmin@chromium.org</owner>
   <summary>
     For parallel downloading, average disk bandwidth seen when only 1 stream is
@@ -13500,6 +13503,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Download.BandwidthWithParallelStreamsBytesPerSecond"
     units="bytes/second">
+  <obsolete>
+    Deprecated April 2017.
+  </obsolete>
   <owner>qinmin@chromium.org</owner>
   <summary>
     For parallel downloading, average disk bandwidth seen when parallel streams
@@ -14027,6 +14033,15 @@ 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.
@@ -124552,7 +124567,7 @@ 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"/>
@@ -124562,6 +124577,25 @@ 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.Counts"/>
+</histogram_suffixes>
+
+<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."/>
+  <affected-histogram name="Download.ParallelizableDownloadBandwidth"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="PasswordCustomPassphrase" separator=".">
   <suffix name="WithCustomPassphrase"/>
   <suffix name="WithoutCustomPassphrase"/>