Add metrics to printer setup flow.

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 5f4ea6b4c6d4365f4b0633e3bf7e3d02fdd9071e..6af39c208f45013791ff37cc390a7fbe8d753feb 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -57069,6 +57069,24 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Printing.CUPS.PpdSource" enum="PpdSource">
+  <owner>skau@chromium.org</owner>
+  <summary>
+    The source of PostScript Printer Description files used during printer
+    setup.  Recorded when a printer is successfully configured.  Only recorded

[Mark P, 2017/05/26 22:57:30]

This statement looks wrong to me.  It looks like the error handling code
OnAddPrinterError() happens after this histogram is emitted.

[skau, 2017/05/26 23:31:51]

The comment has been updated.  We want to track attempted configurations.

+    on Chrome OS.
+  </summary>
+</histogram>
+
+<histogram name="Printing.CUPS.PrinterSetupResult" enum="PrinterSetupResult">
+  <owner>skau@chromium.org</owner>
+  <summary>
+    The success or error code for the set up of a CUPS printer.  Recorded when
+    set up is attempted through the settings dialogs.  Only recorded on Chrome
+    OS.
+  </summary>
+</histogram>
+
 <histogram name="Printing.CUPS.PrintJobsQueued" units="count">
   <owner>skau@chromium.org</owner>
   <summary>