Track printer protocol usage for CUPS printers.

chrome/browser/ui/webui/print_preview/printer_backend_proxy_chromeos.cc

Index: chrome/browser/ui/webui/print_preview/printer_backend_proxy_chromeos.cc
diff --git a/chrome/browser/ui/webui/print_preview/printer_backend_proxy_chromeos.cc b/chrome/browser/ui/webui/print_preview/printer_backend_proxy_chromeos.cc
index a26a8bbc8891c4cd1e3d8b6760c6c7b3800598de..2f21f4506525b1b1a3b53e760711cd07af0a80c8 100644
--- a/chrome/browser/ui/webui/print_preview/printer_backend_proxy_chromeos.cc
+++ b/chrome/browser/ui/webui/print_preview/printer_backend_proxy_chromeos.cc
@@ -11,6 +11,7 @@
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/task_scheduler/post_task.h"
 #include "base/values.h"
 #include "chrome/browser/chromeos/printing/cups_print_job_manager.h"
@@ -123,6 +124,10 @@ class PrinterBackendProxyChromeos : public PrinterBackendProxy {
       return;
     }
 
+    // Log printer configuration for selected printer.
+    UMA_HISTOGRAM_ENUMERATION("CUPS.ProtocolUsed", printer->GetProtocol(),
+                              chromeos::Printer::PROTOCOL_MAX);

[Carlson, 2017/05/25 16:24:35]

Should we be leaving space in the enum for possible future values?

[skau, 2017/05/25 18:49:55]

No.  The max value is just to help in constructing the buckets locally.  We'll
just add values above PROTOCOL_MAX and it'll increment automatically.

+
     if (prefs_->IsConfigurationCurrent(*printer)) {
       // Skip setup if the printer is already installed.
       HandlePrinterSetup(std::move(printer), cb, chromeos::SUCCESS);