Use FileDescriptorWatcher in SerialIoHandlerPosix.

device/serial/serial_io_handler_posix.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_SERIAL_SERIAL_IO_HANDLER_POSIX_H_
 #define DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_
 
+#include <memory>
+
+#include "base/files/file_descriptor_watcher_posix.h"
 #include "base/macros.h"
-#include "base/message_loop/message_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "device/serial/serial_io_handler.h"
 
 namespace device {
 
 // Linux reports breaks and parity errors by inserting the sequence '\377\0x'
 // into the byte stream where 'x' is '\0' for a break and the corrupted byte for
 // a parity error.
 enum class ErrorDetectState { NO_ERROR, MARK_377_SEEN, MARK_0_SEEN };
 
-class SerialIoHandlerPosix : public SerialIoHandler,
-                             public base::MessageLoopForIO::Watcher {
+class SerialIoHandlerPosix : public SerialIoHandler {
  protected:
   // SerialIoHandler impl.
   void ReadImpl() override;
   void WriteImpl() override;
   void CancelReadImpl() override;
   void CancelWriteImpl() override;
   bool ConfigurePortImpl() override;
   bool Flush() const override;
   serial::DeviceControlSignalsPtr GetControlSignals() const override;
   bool SetControlSignals(
       const serial::HostControlSignals& control_signals) override;
   serial::ConnectionInfoPtr GetPortInfo() const override;
   bool SetBreak() override;
   bool ClearBreak() override;
   int CheckReceiveError(char* buffer,
                         int buffer_len,
                         int bytes_read,
                         bool& break_detected,
                         bool& parity_error_detected);
 
  private:
   friend class SerialIoHandler;
   friend class SerialIoHandlerPosixTest;
 
   SerialIoHandlerPosix(
       scoped_refptr<base::SingleThreadTaskRunner> file_thread_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> ui_thread_task_runner);
   ~SerialIoHandlerPosix() override;
 
-  bool AttemptRead(bool within_read);
+  void AttemptRead(bool within_read);
   void RunReadCompleted(bool within_read,
                         int bytes_read,
                         serial::ReceiveError error);
 
-  // base::MessageLoopForIO::Watcher implementation.
-  void OnFileCanWriteWithoutBlocking(int fd) override;
-  void OnFileCanReadWithoutBlocking(int fd) override;
+  // Called when file() is writable without blocking.
+  void OnFileCanWriteWithoutBlocking();
 
   void EnsureWatchingReads();
   void EnsureWatchingWrites();
 
-  base::MessageLoopForIO::FileDescriptorWatcher file_read_watcher_;
-  base::MessageLoopForIO::FileDescriptorWatcher file_write_watcher_;
-
-  // Flags indicating if the message loop is watching the device for IO events.
-  bool is_watching_reads_;
-  bool is_watching_writes_;
+  std::unique_ptr<base::FileDescriptorWatcher::Controller> file_read_watcher_;
+  std::unique_ptr<base::FileDescriptorWatcher::Controller> file_write_watcher_;
 
   ErrorDetectState error_detect_state_;
   bool parity_check_enabled_;
   char chars_stashed_[2];
   int num_chars_stashed_;
 
   DISALLOW_COPY_AND_ASSIGN(SerialIoHandlerPosix);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_