Makes it so mojom files don't need a module

mojo/public/bindings/generators/cpp_templates/module.cc.tmpl

 // Copyright 2013 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.
 
 #if defined(__clang__)
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wunused-private-field"
 #endif
 
 #include "{{module.path}}.h"
 
 #include "mojo/public/cpp/bindings/lib/bindings_serialization.h"
 #include "mojo/public/cpp/bindings/lib/message_builder.h"
 
+{%- if namespace %}
 namespace {{namespace}} {
+{%- endif %}
 namespace internal {
 namespace {
 
 #pragma pack(push, 1)
 
 {#--- Interface parameter definitions #}
 {%- for interface in interfaces %}
 {%-   for method in interface.methods %}
 {%-     set method_name = "k%s_%s_Name"|format(interface.name, method.name) %}
 const uint32_t {{method_name}} = {{method.ordinal}};
@@ skipping 24 matching lines @@
 
 {#--- Struct builder definitions #}
 {%- for struct in structs %}
 {%-   include "struct_builder_definition.tmpl" %}
 {%- endfor %}
 
 {#--- Interface definitions #}
 {%- for interface in interfaces %}
 {%-   include "interface_definition.tmpl" %}
 {%- endfor %}
+{%- if namespace %}
 }  // namespace {{namespace}}
+{%- endif %}
 
 #if defined(__clang__)
 #pragma clang diagnostic pop
 #endif