Add Printing.CUPS.PrintersDiscovered to our metrics.

chrome/browser/chromeos/printing/printer_discoverer.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chromeos/printing/printer_discoverer.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
@@ skipping 57 matching lines @@
   // object.
   void WrappedOnPrintersFound(PrinterDiscoverer::Observer* observer,
                               const std::vector<Printer>& printers) {
     if (observer_list_.HasObserver(observer)) {
       observer->OnPrintersFound(printers);
       // Since USB is the only thing we're worried about at the moment, and we
       // don't have to wait for those printers to be scanned, we can just tell
       // the observer the initial scan is done now.  This will change when we're
       // also doing network discovery -- we'll hold off on issuing this callback
       // until the network discovery is done as well.
-      observer->OnDiscoveryInitialScanDone();
+      observer->OnDiscoveryInitialScanDone(printers.size());
     }
   }
 
   // Get the current set of discovered printers that are not already known
   // to the user's PrintersManager.
   std::vector<Printer> GetAvailablePrinters() {
     // Only know about usb printers for now.  Eventually we'll add discovered
     // network printers as well.
     std::vector<Printer> ret;
     PrintersManager* printers_manager =
@@ skipping 21 matching lines @@
 
 }  // namespace
 
 // static
 std::unique_ptr<PrinterDiscoverer> PrinterDiscoverer::CreateForProfile(
     Profile* profile) {
   return base::MakeUnique<PrinterDiscovererImpl>(profile);
 }
 
 }  // namespace chromeos