[Mojo] Make javascript enums extensible.

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

Index: mojo/public/tools/bindings/generators/js_templates/enum_definition.tmpl
diff --git a/mojo/public/tools/bindings/generators/js_templates/enum_definition.tmpl b/mojo/public/tools/bindings/generators/js_templates/enum_definition.tmpl
index 4ae0a9b5cdb4d3b72e8aab6d64cfc9173211421d..018ca0555496601d6f5f5b6a896c8a097168d27d 100644
--- a/mojo/public/tools/bindings/generators/js_templates/enum_definition.tmpl
+++ b/mojo/public/tools/bindings/generators/js_templates/enum_definition.tmpl
@@ -1,5 +1,5 @@
 {%- macro enum_def(enum_name, enum) -%}
-  {{enum_name}} = {};
+{{enum_name}} = {};
 {%- set prev_enum = 0 %}
 {%- for field in enum.fields %}
 {%-   if field.value %}
@@ -10,4 +10,25 @@
   {{enum_name}}.{{field.name}} = {{enum_name}}.{{enum.fields[loop.index0 - 1].name}} + 1;
 {%-   endif %}
 {%- endfor %}
+
+{{enum_name}}.isKnownEnumValue = function(value) {
+{%-   if enum.fields %}
+      switch (value) {
+{%-     for enum_field in enum.fields|groupby('numeric_value') %}
+        case {{enum_field[0]}}:
+{%-     endfor %}
+          return true;
+      }
+{%-   endif %}
+    return false;
+  };
+
+{{enum_name}}.validate = function(enumValue) {
+    var isExtensible = {% if enum.extensible %}true{% else %}false{% endif %};
+    if (isExtensible || this.isKnownEnumValue(enumValue))
+      return validator.validationError.NONE;
+
+    return validator.validationError.UNKNOWN_ENUM_VALUE;
+  };
+
 {%- endmacro %}