Record print job success and print queue size.

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 7de5ee9588f25c6f8f38940f6919a63cce2fdb85..bb9979cb5a6ade0e6080dd8c6ea5dc4912e1ef55 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -9815,6 +9815,22 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="CUPS.JobResult" enum="PrintJobResult">

[Alexei Svitkine (slow), 2017/05/25 15:13:56]

Suggest using a more general top-level prefix, like Printing.

e.g. Printing.CUPS.JobResult

[skau, 2017/05/25 18:45:40]

Done.

+  <owner>skau@chromium.org</owner>
+  <summary>
+    The final status of every print job that was succesfully queued.  Only used
+    on Chrome OS.
+  </summary>
+</histogram>
+
+<histogram name="CUPS.PrintJobsQueued" units="count">
+  <owner>skau@chromium.org</owner>
+  <summary>
+    The size of the print queue when a print job is initially queued.  When the
+    first job is started, a zero is recorded.  Only used on Chrome OS.
+  </summary>
+</histogram>
+
 <histogram name="CustomTabs.ClientAppId" enum="ClientAppId">
   <owner>yusufo@chromium.org</owner>
   <summary>