Makes it so mojom files don't need a module

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

Index: mojo/public/bindings/generators/cpp_templates/module.cc.tmpl
diff --git a/mojo/public/bindings/generators/cpp_templates/module.cc.tmpl b/mojo/public/bindings/generators/cpp_templates/module.cc.tmpl
index 33bd46bcd0c79a5b1d93a3abc50887da06465bf1..d99a3e2424ac921fff19a65197fc9a6c98ba7165 100644
--- a/mojo/public/bindings/generators/cpp_templates/module.cc.tmpl
+++ b/mojo/public/bindings/generators/cpp_templates/module.cc.tmpl
@@ -12,7 +12,9 @@
 #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 {
 
@@ -57,7 +59,9 @@ const uint32_t {{method_name}} = {{method.ordinal}};
 {%- for interface in interfaces %}
 {%-   include "interface_definition.tmpl" %}
 {%- endfor %}
+{%- if namespace %}
 }  // namespace {{namespace}}
+{%- endif %}
 
 #if defined(__clang__)
 #pragma clang diagnostic pop