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

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

 // 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.
 
 #include "chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/files/file_util.h"
 #include "base/json/json_string_value_serializer.h"
 #include "base/memory/ptr_util.h"
 #include "base/path_service.h"
 #include "base/strings/string_util.h"
 #include "base/threading/sequenced_task_runner_handle.h"
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
-#include "chrome/browser/chromeos/printing/fake_printer_discoverer.h"
 #include "chrome/browser/chromeos/printing/ppd_provider_factory.h"
 #include "chrome/browser/chromeos/printing/printer_configurer.h"
+#include "chrome/browser/chromeos/printing/printer_discoverer.h"
 #include "chrome/browser/chromeos/printing/printers_manager_factory.h"
 #include "chrome/browser/download/download_prefs.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/chrome_select_file_policy.h"
 #include "chrome/common/chrome_paths.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/debug_daemon_client.h"
 #include "chromeos/printing/ppd_cache.h"
@@ skipping 339 matching lines @@
 void CupsPrintersHandler::FileSelected(const base::FilePath& path,
                                        int index,
                                        void* params) {
   DCHECK(!webui_callback_id_.empty());
   ResolveJavascriptCallback(base::Value(webui_callback_id_),
                             base::Value(path.value()));
   webui_callback_id_.clear();
 }
 
 void CupsPrintersHandler::HandleStartDiscovery(const base::ListValue* args) {
-  if (!printer_discoverer_.get())
-    printer_discoverer_ = chromeos::PrinterDiscoverer::Create();
+  if (!printer_discoverer_.get()) {
+    printer_discoverer_ =
+        chromeos::PrinterDiscoverer::CreateForProfile(profile_);
+  }
 
   printer_discoverer_->AddObserver(this);
-  if (!printer_discoverer_->StartDiscovery()) {
-    CallJavascriptFunction("cr.webUIListenerCallback",
-                           base::Value("on-printer-discovery-failed"));
-    printer_discoverer_->RemoveObserver(this);
-  }
 }
 
 void CupsPrintersHandler::HandleStopDiscovery(const base::ListValue* args) {
-  if (printer_discoverer_.get()) {
-    printer_discoverer_->RemoveObserver(this);
-    printer_discoverer_->StopDiscovery();
-    printer_discoverer_.reset();
-  }
+  printer_discoverer_.reset();
 }
 
 void CupsPrintersHandler::OnPrintersFound(
     const std::vector<Printer>& printers) {
   std::unique_ptr<base::ListValue> printers_list =
       base::MakeUnique<base::ListValue>();
   for (const auto& printer : printers) {
-    std::unique_ptr<base::DictionaryValue> printer_info =
-        GetPrinterInfo(printer);
-    printers_list->Append(std::move(printer_info));
+    printers_list->Append(GetPrinterInfo(printer));
   }
 
   CallJavascriptFunction("cr.webUIListenerCallback",
                          base::Value("on-printer-discovered"), *printers_list);
 }
 
-void CupsPrintersHandler::OnDiscoveryDone() {
+void CupsPrintersHandler::OnDiscoveryInitialScanDone() {
   CallJavascriptFunction("cr.webUIListenerCallback",
                          base::Value("on-printer-discovery-done"));
 }
 
 }  // namespace settings
 }  // namespace chromeos