Use the task scheduler for blocking tasks in the USB service on Linux

device/usb/usb_device_linux.h

 // Copyright 2014 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 DEVICE_USB_USB_DEVICE_IMPL_H_
 #define DEVICE_USB_USB_DEVICE_IMPL_H_
 
 #include <stdint.h>
 
 #include <string>
 #include <utility>
 
 #include "base/files/scoped_file.h"
 #include "base/macros.h"
-#include "base/threading/thread_checker.h"
+#include "base/sequence_checker.h"
 #include "build/build_config.h"
 #include "device/usb/usb_device.h"
 #include "device/usb/webusb_descriptors.h"
 
 namespace base {
 class SequencedTaskRunner;
 }
 
 namespace device {
 
@@ skipping 19 matching lines @@
 
  protected:
   friend class UsbServiceLinux;
 
   // Called by UsbServiceLinux only.
   UsbDeviceLinux(const std::string& device_path,
                  const UsbDeviceDescriptor& descriptor,
                  const std::string& manufacturer_string,
                  const std::string& product_string,
                  const std::string& serial_number,
-                 uint8_t active_configuration,
-                 scoped_refptr<base::SequencedTaskRunner> blocking_task_runner);
+                 uint8_t active_configuration);
 
   ~UsbDeviceLinux() override;
 
  private:
 #if defined(OS_CHROMEOS)
   void OnOpenRequestComplete(const OpenCallback& callback, base::ScopedFD fd);
   void OnOpenRequestError(const OpenCallback& callback,
                           const std::string& error_name,
                           const std::string& error_message);
 #else
-  void OpenOnBlockingThread(const OpenCallback& callback);
+  void OpenOnBlockingThread(
+      const OpenCallback& callback,
+      scoped_refptr<base::SequencedTaskRunner> task_runner,
+      scoped_refptr<base::SequencedTaskRunner> blocking_task_runner);
 #endif  // defined(OS_CHROMEOS)
-  void Opened(base::ScopedFD fd, const OpenCallback& callback);
+  void Opened(base::ScopedFD fd,
+              const OpenCallback& callback,
+              scoped_refptr<base::SequencedTaskRunner> blocking_task_runner);
 
-  base::ThreadChecker thread_checker_;
+  base::SequenceChecker sequence_checker_;
 
   const std::string device_path_;
 
-  scoped_refptr<base::SequencedTaskRunner> task_runner_;
-  scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
-
   DISALLOW_COPY_AND_ASSIGN(UsbDeviceLinux);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_USB_USB_DEVICE_IMPL_H_