Mojo C++ bindings: remove the lock in MultiplexRouter if it only serves a single interface.

mojo/public/cpp/bindings/BUILD.gn

 # Copyright 2014 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.
 
 static_library("bindings") {
   sources = [
     "array.h",
     "array_data_view.h",
     "array_traits.h",
     "array_traits_carray.h",
@@ skipping 37 matching lines @@
     "lib/control_message_proxy.cc",
     "lib/control_message_proxy.h",
     "lib/filter_chain.cc",
     "lib/fixed_buffer.cc",
     "lib/fixed_buffer.h",
     "lib/handle_interface_serialization.h",
     "lib/interface_endpoint_client.cc",
     "lib/interface_ptr_state.h",
     "lib/map_data_internal.h",
     "lib/map_serialization.h",
+    "lib/may_auto_lock.h",
     "lib/message.cc",
     "lib/message_buffer.cc",
     "lib/message_buffer.h",
     "lib/message_builder.cc",
     "lib/message_builder.h",
     "lib/message_header_validator.cc",
     "lib/message_internal.h",
     "lib/multiplex_router.cc",
     "lib/multiplex_router.h",
     "lib/native_enum_data.h",
@@ skipping 96 matching lines @@
     ]
 
     public_deps = [
       ":bindings",
       "//third_party/WebKit/Source/wtf",
     ]
 
     public_configs = [ "//third_party/WebKit/Source:config" ]
   }
 }