Add Printing.CUPS.PrintersDiscovered to our metrics.

chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.h

Index: chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.h
diff --git a/chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.h b/chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.h
index 4004a5e45fcbafe174604684734192cee31109af..13ebf24db70ce7e492d299755c5e2d6b889c6241 100644
--- a/chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.h
+++ b/chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.h
@@ -87,8 +87,8 @@ class CupsPrintersHandler : public ::settings::SettingsPageUIHandler,
   void HandleStopDiscovery(const base::ListValue* args);
 
   // chromeos::PrinterDiscoverer::Observer override:
-  void OnPrintersFound(const std::vector<Printer>& printers) override;
-  void OnDiscoveryInitialScanDone() override;
+  void OnPrintersFound(bool scan_done,
+                       const std::vector<Printer>& printers) override;
 
   // Invokes debugd to add the printer to CUPS.  If |ipp_everywhere| is true,
   // automatic configuration will be attempted  and |ppd_path| is ignored.