Move IPC::MessageFilter and router to a separate file

ipc/BUILD.gn

 # 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.
 
 component("ipc") {
   sources = [
     "file_descriptor_set_posix.cc",
     "file_descriptor_set_posix.h",
     "ipc_channel.cc",
     "ipc_channel.h",
@@ skipping 28 matching lines @@
     "ipc_platform_file.h",
     "ipc_sender.h",
     "ipc_switches.cc",
     "ipc_switches.h",
     "ipc_sync_channel.cc",
     "ipc_sync_channel.h",
     "ipc_sync_message.cc",
     "ipc_sync_message.h",
     "ipc_sync_message_filter.cc",
     "ipc_sync_message_filter.h",
+    "message_filter.cc",
+    "message_filter.h",
+    "message_filter_router.cc",
+    "message_filter_router.h",
     "param_traits_log_macros.h",
     "param_traits_macros.h",
     "param_traits_read_macros.h",
     "param_traits_write_macros.h",
     "struct_constructor_macros.h",
     "struct_destructor_macros.h",
     "unix_domain_socket_util.cc",
     "unix_domain_socket_util.h",
   ]
 
@@ skipping 107 matching lines @@
     "ipc_test_sink.cc",
     "ipc_test_sink.h",
   ]
   deps = [
     ":ipc",
     "//base",
     "//testing/gtest",
   ]
 }