Remove handler from MessagePumpForIO::IOContext.

device/serial/serial_io_handler_win.cc

Index: device/serial/serial_io_handler_win.cc
diff --git a/device/serial/serial_io_handler_win.cc b/device/serial/serial_io_handler_win.cc
index 4c1010fbd833069eea446b172a5603502a28c2dd..1df4c3662828da9fc570c13e51e2c81433c2cd87 100644
--- a/device/serial/serial_io_handler_win.cc
+++ b/device/serial/serial_io_handler_win.cc
@@ -239,16 +239,8 @@ bool SerialIoHandlerWin::PostOpen() {
                                                        this);
 
   comm_context_.reset(new base::MessageLoopForIO::IOContext());
-  comm_context_->handler = this;
-  memset(&comm_context_->overlapped, 0, sizeof(comm_context_->overlapped));
-
   read_context_.reset(new base::MessageLoopForIO::IOContext());
-  read_context_->handler = this;
-  memset(&read_context_->overlapped, 0, sizeof(read_context_->overlapped));
-
   write_context_.reset(new base::MessageLoopForIO::IOContext());
-  write_context_->handler = this;
-  memset(&write_context_->overlapped, 0, sizeof(write_context_->overlapped));
 
   scoped_refptr<base::SingleThreadTaskRunner> io_thread_task_runner =
       base::ThreadTaskRunnerHandle::Get();