Remove the mojo serial interfaces and related infrastructure.

device/serial/BUILD.gn

Index: device/serial/BUILD.gn
diff --git a/device/serial/BUILD.gn b/device/serial/BUILD.gn
index 8d2b4f0a8c70466895e2b3246c583474a80f232a..9679a65df452c6084a1e32363a1bec8b58463b05 100644
--- a/device/serial/BUILD.gn
+++ b/device/serial/BUILD.gn
@@ -22,18 +22,6 @@ static_library("serial") {
   sources = [
     "buffer.cc",
     "buffer.h",
-    "data_receiver.cc",
-    "data_receiver.h",
-    "data_sender.cc",
-    "data_sender.h",
-    "data_sink_receiver.cc",
-    "data_sink_receiver.h",
-    "data_source_sender.cc",
-    "data_source_sender.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",
@@ -48,8 +36,6 @@ static_library("serial") {
     "serial_io_handler_posix.h",
     "serial_io_handler_win.cc",
     "serial_io_handler_win.h",
-    "serial_service_impl.cc",
-    "serial_service_impl.h",
   ]
 
   public_configs = [ ":platform_support" ]
@@ -101,10 +87,7 @@ mojom("serial_mojo") {
   ]
 
   sources = [
-    "data_stream.mojom",
-    "data_stream_serialization.mojom",
     "serial.mojom",
-    "serial_serialization.mojom",
   ]
 
   use_new_wrapper_types = false