Use a JS dictionary to initialize a the fields in a Mojo struct

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

Index: mojo/public/tools/bindings/generators/js_templates/struct_definition.tmpl
diff --git a/mojo/public/tools/bindings/generators/js_templates/struct_definition.tmpl b/mojo/public/tools/bindings/generators/js_templates/struct_definition.tmpl
index df3ee17e4049a351c3bc56d3df361a58629aa820..d77b28b80eaf9bc739eff75e89cde43aa6e471d0 100644
--- a/mojo/public/tools/bindings/generators/js_templates/struct_definition.tmpl
+++ b/mojo/public/tools/bindings/generators/js_templates/struct_definition.tmpl
@@ -1,26 +1,35 @@
 {#--- Begin #}
-  function {{struct.name}}() {
+  function {{struct.name}}(values) {
     this.initDefaults_();
+    this.initFields_(values);
   }
 
 {#--- Enums #}
 {%- from "enum_definition.tmpl" import enum_def %}
 {%  for enum in struct.enums %}
   {{enum_def("%s.%s"|format(struct.name, enum.name), enum, module)}}
-{%  endfor %}
+{%-  endfor %}
 
 {#--- Constants #}
 {%  for constant in struct.constants %}
   {{struct.name}}.{{constant.name}} = {{constant.value|expression_to_text}};
-{%  endfor %}
+{%-  endfor %}
 
-{#--- Set up defaults #}
+{#--- initDefaults() #}
   {{struct.name}}.prototype.initDefaults_ = function() {
 {%- for packed_field in struct.packed.packed_fields %}
     this.{{packed_field.field.name}} = {{packed_field.field|default_value}};
 {%- endfor %}
   };
 
+{#--- initFields() #}
+  {{struct.name}}.prototype.initFields_ = function(fields) {
+    for(var field in fields) {
+        if (this.hasOwnProperty(field))
+          this[field] = fields[field];
+    }
+  };
+
 {#--- Validation #}
 
   {{struct.name}}.validate = function(messageValidator, offset) {