Add support for enums within structs and interfaces to mojom.

mojo/public/bindings/generators/js_templates/interface_definition.tmpl

 {%- for method in interface.methods %}
   var k{{interface.name}}_{{method.name}}_Name = {{method.ordinal}};
 {%- endfor %}
 
   function {{interface.name}}Proxy(receiver) {
     this.receiver_ = receiver;
   }
 
 {%- for method in interface.methods %}
   {{interface.name}}Proxy.prototype.{{method.name|stylize_method}} = function(
@@ skipping 26 matching lines @@
       this.{{method.name|stylize_method}}(
 {%- for parameter in method.parameters -%}
 params.{{parameter.name}}{% if not loop.last %}, {% endif %}
 {%- endfor %});
       return true;
 {%- endfor %}
     default:
       return false;
     }
   };
+
+{#--- Enums #}
+{%- from "enum_definition.tmpl" import enum_def -%}
+{%  for enum in interface.enums %}
+{{  enum_def("%sProxy.%s"|format(interface.name, enum.name), enum)}}
+  {{interface.name}}Stub.{{enum.name}} = {{interface.name}}Proxy.{{enum.name}};
+{%-  endfor %}