Pull in mtpd from CrOS and add files to build it on Linux.

third_party/mtpd/mtpd.gyp

+# 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.
+
+{
+  'targets': [
+    {
+      'target_name': 'mtpd',
+      'type': 'executable',
+      'dependencies': [
+        '../../base/base.gyp:base',
+        '../../build/linux/system.gyp:udev',
+        '../../chrome/chrome.gyp:mtp_file_entry_proto',
+        '../../chrome/chrome.gyp:mtp_storage_info_proto',
+        '../../third_party/cros_dbus_cplusplus/cros_dbus_cplusplus.gyp:dbus_cplusplus',
+        '../../third_party/libmtp/libmtp.gyp:libmtp',
+      ],
+      'sources': [
+        'source/assert_matching_file_types.cc',
+        'source/build_config.h',
+        'source/daemon.cc',
+        'source/daemon.h',
+        'source/device_event_delegate.h',
+        'source/device_manager.cc',
+        'source/device_manager.h',
+        'source/file_entry.cc',
+        'source/file_entry.h',
+        'source/main.cc',
+        'source/mtpd_server_impl.cc',
+        'source/mtpd_server_impl.h',
+        'source/service_constants.h',
+        'source/storage_info.cc',
+        'source/storage_info.h',
+        'source/string_helpers.cc',
+        'source/string_helpers.h',
+      ],
+      'include_dirs': [
+        '.',
+        '<(SHARED_INTERMEDIATE_DIR)/protoc_out/chrome/browser/media_transfer_protocol',
+      ],
+    },
+  ],
+}