Record more download resumption UMAs to analyze the how download is resumed

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..0b0fc3598b08394d212b7c92d1d7b5cb42332a11 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -30129,6 +30129,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="MobileDownload.ResumptionsCount">

[Ilya Sherman, 2017/04/17 22:18:43]

nit: Please add base="true", as this histogram name is not emitted to directly;
it's just used for building up suffixes.

[qinmin, 2017/04/17 23:41:53]

Done.

+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Android: Records the number of resumptions for a download by resumption
+    type.

[Ilya Sherman, 2017/04/17 22:18:43]

Please document when this is recorded: On each resumption?  When the download
completes? (successfully? in failure?)

[qinmin, 2017/04/17 23:41:53]

Done.

+  </summary>
+</histogram>
+
 <histogram name="MobileFre.Progress" enum="MobileFreProgress">
   <owner>gogerald@chromium.org</owner>
   <summary>
@@ -120388,6 +120396,13 @@ from previous Chrome versions.
   <affected-histogram name="MobileDownload.InterruptionsCount"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="MobileDownloadResumptionsCountTypes" separator=".">
+  <suffix name="Automatic"/>
+  <suffix name="Manual"/>
+  <suffix name="Total"/>
+  <affected-histogram name="MobileDownload.ResumptionsCount"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="MobileFreEntryType" separator=".">
   <suffix name="MainIntent" label="Icon click"/>
   <suffix name="ViewIntent" label="VIEW intent"/>