[Mojo] Make javascript enums extensible.

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

 {%- macro enum_def(enum_name, enum) -%}
-  {{enum_name}} = {};
+{{enum_name}} = {};
 {%- set prev_enum = 0 %}
 {%- for field in enum.fields %}
 {%-   if field.value %}
   {{enum_name}}.{{field.name}} = {{field.value|expression_to_text}};
 {%-   elif loop.first %}
   {{enum_name}}.{{field.name}} = 0;
 {%-   else %}
   {{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) {

[Ken Rockot(use gerrit already), 2016/09/30 21:51:54]

nit: 2 space indentation, not 4. Note, the jinja indentation and the templated
code indentation are independent. the jinja "if" indent is correct on the line
above, but this line should be indented  with respect to the function { block
containing it. Same indentation change applies to the rest of this generated
function and the one below.


foo = function(...) {
  // two spaces
};

+{%-     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 %}