Mojo JS bindings: add support to generate "dual-mode" code.

mojo/public/tools/bindings/generators/js_templates/module_definition.tmpl

 {#--- Constants #}
 {%- for constant in module.constants %}
   var {{constant.name}} = {{constant.value|expression_to_text}};
 {%- endfor %}
 
 {#--- Enums #}
 {%- from "enum_definition.tmpl" import enum_def %}
 {%- for enum in enums %}
   var {{ enum_def(enum.name, enum) }}
 {%-  endfor %}
 
 {#--- Struct definitions #}
 {%  for struct in structs %}
 {%-   include "struct_definition.tmpl" %}
 {%- endfor -%}
 
 {#--- Union definitions #}
 {%- from "union_definition.tmpl" import union_def %}
 {%- for union in unions %}
 {{union_def(union)|indent(2)}}
 {%- endfor %}
 
 {#--- Interface definitions #}
 {%- for interface in interfaces -%}
 {%-   include "interface_definition.tmpl" %}
 {%- endfor %}
 
-{%- if use_new_js_bindings %}
-  var exports = mojo.internal.exposeNamespace("{{module.namespace}}");
-{%- else %}
-  var exports = {};
-{%- endif %}
-
 {%- for constant in module.constants %}
   exports.{{constant.name}} = {{constant.name}};
 {%- endfor %}
 {%- for enum in enums %}
   exports.{{enum.name}} = {{enum.name}};
 {%- endfor %}
 {%- for struct in structs if struct.exported %}
   exports.{{struct.name}} = {{struct.name}};
 {%- endfor %}
 {%- for union in unions %}
   exports.{{union.name}} = {{union.name}};
 {%- endfor %}
 {%- for interface in interfaces %}
   exports.{{interface.name}} = {{interface.name}};
   exports.{{interface.name}}Ptr = {{interface.name}}Ptr;
   exports.{{interface.name}}AssociatedPtr = {{interface.name}}AssociatedPtr;
 {%- endfor %}