Make CUPS USB printing play better with the settings page. This change does several things:

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

 // Copyright 2016 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_SETTINGS_CHROMEOS_CUPS_PRINTERS_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_CHROMEOS_CUPS_PRINTERS_HANDLER_H_
 
 #include <memory>
 #include <string>
 #include <vector>
@@ skipping 70 matching lines @@
   // ui::SelectFileDialog::Listener override:
   void FileSelected(const base::FilePath& path,
                     int index,
                     void* params) override;
 
   void HandleStartDiscovery(const base::ListValue* args);
   void HandleStopDiscovery(const base::ListValue* args);
 
   // chromeos::PrinterDiscoverer::Observer override:
   void OnPrintersFound(const std::vector<Printer>& printers) override;
-  void OnDiscoveryDone() override;
+  void OnDiscoveryInitialScanDone() override;
 
   // Invokes debugd to add the printer to CUPS.  If |ipp_everywhere| is true,
   // automatic configuration will be attempted  and |ppd_path| is ignored.
   // |ppd_path| is the path to a Postscript Printer Description file that will
   // be used to configure the printer capabilities.  This file must be in
   // Downloads or the PPD Cache.
   void AddPrinterToCups(std::unique_ptr<Printer> printer,
                         const base::FilePath& ppd_path,
                         bool ipp_everywhere);
 
@@ skipping 12 matching lines @@
 
   base::WeakPtrFactory<CupsPrintersHandler> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CupsPrintersHandler);
 };
 
 }  // namespace settings
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_CHROMEOS_CUPS_PRINTERS_HANDLER_H_