Never lock the Pepper proxy lock on the IO thread

ppapi/proxy/BUILD.gn

 # Copyright 2015 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.
 
 config("proxy_implementation") {
   defines = [ "PPAPI_PROXY_IMPLEMENTATION" ]
 }
 
 component("proxy") {
   output_name = "ppapi_proxy"
@@ skipping 145 matching lines @@
     "tcp_socket_private_resource.cc",
     "tcp_socket_private_resource.h",
     "tcp_socket_resource.cc",
     "tcp_socket_resource.h",
     "tcp_socket_resource_base.cc",
     "tcp_socket_resource_base.h",
     "truetype_font_resource.cc",
     "truetype_font_resource.h",
     "truetype_font_singleton_resource.cc",
     "truetype_font_singleton_resource.h",
+    "udp_socket_filter.cc",
+    "udp_socket_filter.h",
     "udp_socket_private_resource.cc",
     "udp_socket_private_resource.h",
     "udp_socket_resource.cc",
     "udp_socket_resource.h",
     "udp_socket_resource_base.cc",
     "udp_socket_resource_base.h",
     "uma_private_resource.cc",
     "uma_private_resource.h",
     "url_loader_resource.cc",
     "url_loader_resource.h",
@@ skipping 171 matching lines @@
   deps = [
     "//base/test:test_support",
     "//ipc",
     "//ipc:test_support",
     "//ppapi/proxy",
     "//ppapi/shared_impl",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }