Mojo: Add support for constants to the IDL compiler.

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

Index: mojo/public/tools/bindings/generators/js_templates/module.js.tmpl
diff --git a/mojo/public/tools/bindings/generators/js_templates/module.js.tmpl b/mojo/public/tools/bindings/generators/js_templates/module.js.tmpl
index 9b3046825c1d13e1efd24068d3a9e7fb74866087..aaa3ed557f7520e4111dd7a6b52f6df5ecf2fe6b 100644
--- a/mojo/public/tools/bindings/generators/js_templates/module.js.tmpl
+++ b/mojo/public/tools/bindings/generators/js_templates/module.js.tmpl
@@ -14,9 +14,14 @@ define("{{module.path}}", [
 {%- endfor -%}
 ) {
 
+{#--- Constants #}
+{%  for constant in module.constants %}
+  var {{constant.name}} = {{constant.value|expression_to_text(module)}};
+{%- endfor %}
+
 {#--- Enums #}
-{%  from "enum_definition.tmpl" import enum_def -%}
-{%  for enum in enums %}
+{%- from "enum_definition.tmpl" import enum_def %}
+{%- for enum in enums %}
   var {{ enum_def(enum.name, enum, module) }}
 {%-  endfor %}
 
@@ -31,6 +36,9 @@ define("{{module.path}}", [
 {%- endfor %}
 
   var exports = {};
+{%  for constant in module.constants %}
+  exports.{{constant.name}} = {{constant.name}};
+{%- endfor %}
 {%- for enum in enums %}
   exports.{{enum.name}} = {{enum.name}};
 {%- endfor %}