Move more printing code off of the FILE thread.

chrome/browser/printing/printer_manager_dialog_linux.cc

 // Copyright (c) 2012 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 <memory>
 
 #include "base/bind.h"
 #include "base/environment.h"
 #include "base/files/file_util.h"
-#include "base/message_loop/message_loop.h"
 #include "base/nix/xdg_util.h"
 #include "base/process/kill.h"
 #include "base/process/launch.h"
-#include "base/strings/string_split.h"
-#include "content/public/browser/browser_thread.h"
-
-using base::Environment;
-using content::BrowserThread;
+#include "base/task_scheduler/post_task.h"
+#include "base/threading/thread_restrictions.h"
 
 namespace {
 
 // KDE printer config command ("system-config-printer-kde") causes the
 // OptionWidget to crash (https://bugs.kde.org/show_bug.cgi?id=271957).
 // Therefore, use GNOME printer config command for KDE.
 const char* const kSystemConfigPrinterCommand[] = {"system-config-printer",
                                                    nullptr};
 
 const char* const kGnomeControlCenterPrintersCommand[] = {
@@ skipping 11 matching lines @@
   base::Process process = base::LaunchProcess(argv, base::LaunchOptions());
   if (!process.IsValid())
     return false;
   base::EnsureProcessGetsReaped(process.Pid());
   return true;
 }
 
 // Detect the command based on the deskop environment and open the printer
 // manager dialog.
 void DetectAndOpenPrinterConfigDialog() {
-  DCHECK_CURRENTLY_ON(BrowserThread::FILE);
-  std::unique_ptr<Environment> env(Environment::Create());
+  base::ThreadRestrictions::AssertIOAllowed();
+  std::unique_ptr<base::Environment> env(base::Environment::Create());
 
   bool opened = false;
   switch (base::nix::GetDesktopEnvironment(env.get())) {
     case base::nix::DESKTOP_ENVIRONMENT_GNOME:
       opened = OpenPrinterConfigDialog(kSystemConfigPrinterCommand) ||
                OpenPrinterConfigDialog(kGnomeControlCenterPrintersCommand);
       break;
     case base::nix::DESKTOP_ENVIRONMENT_KDE3:
     case base::nix::DESKTOP_ENVIRONMENT_KDE4:
     case base::nix::DESKTOP_ENVIRONMENT_KDE5:
     case base::nix::DESKTOP_ENVIRONMENT_UNITY:
     case base::nix::DESKTOP_ENVIRONMENT_XFCE:
       opened = OpenPrinterConfigDialog(kSystemConfigPrinterCommand);
       break;
     case base::nix::DESKTOP_ENVIRONMENT_OTHER:
       LOG(ERROR)
           << "Failed to detect the command to open printer config dialog";
       return;
   }
   LOG_IF(ERROR, !opened) << "Failed to open printer manager dialog ";
 }
 
-}  // anonymous namespace
+}  // namespace
 
 namespace printing {
 
 void PrinterManagerDialog::ShowPrinterManagerDialog() {
-  BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
-                          base::BindOnce(&DetectAndOpenPrinterConfigDialog));
+  base::PostTaskWithTraits(
+      FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_BLOCKING},
+      base::BindOnce(&DetectAndOpenPrinterConfigDialog));
 }
 
 }  // namespace printing