Move more printing code off of the FILE thread.

chrome/browser/printing/printer_manager_dialog_win.cc

 // Copyright (c) 2011 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/printing/printer_manager_dialog.h"
 
 #include <windows.h>
 #include <shellapi.h>
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/path_service.h"
+#include "base/task_scheduler/post_task.h"
 #include "base/threading/thread.h"
-#include "chrome/browser/browser_process.h"
-#include "content/public/browser/browser_thread.h"
 
-using content::BrowserThread;
-
-namespace printing {
+namespace {
 
 // A helper callback that opens the printer management dialog.
 void OpenPrintersDialogCallback() {
   base::FilePath sys_dir;
   PathService::Get(base::DIR_SYSTEM, &sys_dir);
-  base::FilePath rundll32 = sys_dir.AppendASCII("rundll32.exe");
-  base::FilePath shell32dll = sys_dir.AppendASCII("shell32.dll");
+  base::FilePath rundll32 = sys_dir.Append(L"rundll32.exe");
+  base::FilePath shell32dll = sys_dir.Append(L"shell32.dll");
 
   std::wstring args(shell32dll.value());
   args.append(L",SHHelpShortcuts_RunDLL PrintersFolder");
-  ShellExecute(NULL, L"open", rundll32.value().c_str(), args.c_str(), NULL,
-               SW_SHOWNORMAL);
+  ShellExecute(nullptr, L"open", rundll32.value().c_str(), args.c_str(),
+               nullptr, SW_SHOWNORMAL);
 }
 
+}  // namespace
+
+namespace printing {
+
 void PrinterManagerDialog::ShowPrinterManagerDialog() {
-  BrowserThread::PostTask(
-      BrowserThread::FILE,
-      FROM_HERE,
+  base::PostTaskWithTraits(
+      FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_BLOCKING},
       base::Bind(OpenPrintersDialogCallback));
 }
 
 }  // namespace printing