Convert SerialIoHandler to use buffer interfaces for I/O API methods.

device/serial/BUILD.gn

 # 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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 # GYP version: device/serial/serial.gyp:device_serial
 static_library("serial") {
   output_name = "device_serial"
 
   sources = [
+    "buffer.cc",
+    "buffer.h",
     "serial_connection.cc",
     "serial_connection.h",
     "serial_connection_factory.cc",
     "serial_connection_factory.h",
     "serial_device_enumerator.cc",
     "serial_device_enumerator.h",
     "serial_device_enumerator_linux.cc",
     "serial_device_enumerator_linux.h",
     "serial_device_enumerator_mac.cc",
     "serial_device_enumerator_mac.h",
@@ skipping 36 matching lines @@
 mojom("serial_mojo") {
   visibility = [
     ":serial",
     "//extensions:extensions_renderer_resources_grit",
   ]
 
   sources = [
     "serial.mojom",
   ]
 }