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

mojo/public/tools/bindings/generators/js_templates/module.amd.tmpl

 // 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.
 
-{%- if use_new_js_bindings %}
+{%- if js_bindings_mode == "both" or js_bindings_mode == "new" %}
+{{"new"|set_current_mode}}
 
 'use strict';
 
+{%-   if js_bindings_mode == "both" %}
+if (mojo && mojo.internal && mojo.config) {
+{%-   endif %}
+
 (function() {
   var mojomId = '{{module.path}}';
   if (mojo.internal.isMojomLoaded(mojomId)) {
     console.warn('The following mojom is loaded multiple times: ' + mojomId);
     return;
   }
   mojo.internal.markMojomLoaded(mojomId);
 
   // TODO(yzshen): Define these aliases to minimize the differences between the
   // old/new modes. Remove them when the old mode goes away.
   var bindings = mojo;
   var associatedBindings = mojo;
   var codec = mojo.internal;
   var validator = mojo.internal;
 
 {%-   for import in imports %}
   var {{import.unique_name}} =
       mojo.internal.exposeNamespace('{{import.namespace}}');
   if (mojo.config.autoLoadMojomDeps) {
     mojo.internal.loadMojomIfNecessary(
         '{{import.path}}',
         new URL('{{import|get_relative_url(module)}}.js',
                 document.currentScript.src).href);
   }
 {%-   endfor %}
 
 {% include "module_definition.tmpl" %}
 })();
 
-{%- else %}
+{%-   if js_bindings_mode == "both" %}
+}
+{%-   endif %}
+
+{%- endif %}
+
+{%- if js_bindings_mode == "both" or js_bindings_mode == "old" %}
+{{"old"|set_current_mode}}
+
+{%-   if js_bindings_mode == "both" %}
+if (!mojo || !mojo.internal || !mojo.config) {
+{%-   endif %}
 
 define("{{module.path}}", [
 {%- if module.path !=
          "mojo/public/interfaces/bindings/interface_control_messages.mojom" and
        module.path !=
          "mojo/public/interfaces/bindings/pipe_control_messages.mojom" %}
     "mojo/public/js/associated_bindings",
     "mojo/public/js/bindings",
 {%-   endif %}
     "mojo/public/js/codec",
@@ skipping 12 matching lines @@
 {%-   for import in imports -%}
     , {{import.unique_name}}
 {%-   endfor -%}
 ) {
 
 {%- include "module_definition.tmpl" %}
 
   return exports;
 });
 
+{%-   if js_bindings_mode == "both" %}
+}
+{%-   endif %}
+
 {%- endif %}