Remove MTP support on Linux.

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index b5a05cfca028c69c1a7aaa0d780de1fa981e1d5e..fd31690e99dc86c161f99d9e29f25f85e28cb218 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -3500,7 +3500,6 @@ test("unit_tests") {
       "../browser/media/webrtc/tab_desktop_media_list_unittest.cc",
       "../browser/media_galleries/fileapi/native_media_file_util_unittest.cc",
       "../browser/media_galleries/gallery_watch_manager_unittest.cc",
-      "../browser/media_galleries/linux/mtp_device_object_enumerator_unittest.cc",
       "../browser/media_galleries/mac/mtp_device_delegate_impl_mac_unittest.mm",
       "../browser/media_galleries/media_file_system_registry_unittest.cc",
       "../browser/media_galleries/media_galleries_dialog_controller_mock.cc",
@@ -3855,6 +3854,7 @@ test("unit_tests") {
       "../browser/extensions/zipfile_installer_unittest.cc",
       "../browser/media/cast_remoting_sender_unittest.cc",
       "../browser/media/cast_transport_host_filter_unittest.cc",
+      "../browser/media_galleries/chromeos/mtp_device_object_enumerator_unittest.cc",
       "../browser/metrics/extensions_metrics_provider_unittest.cc",
       "../browser/notifications/extension_welcome_notification_unittest.cc",
       "../browser/notifications/notification_conversion_helper_unittest.cc",