Add support for named arguments to our bindings generation.

sky/engine/bindings/scripts/templates/interface_dart.template

 // Copyright 2015 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.
 
 // WARNING: Do not edit - generated code.
 part of sky.core;
 
-abstract class {{interface_name}} extends {{ parent_interface if parent_interface else 'NativeFieldWrapperClass2' }} {
-
 {% macro args_macro(args) -%}
     {%- for arg in args -%}
         {%- if arg.is_optional and (loop.first or not args[arg.index-1].is_optional) -%}
-        [
+        {{ '{' if arg.is_named else '[' }}
         {%- endif -%}
         {{ arg.dart_type }} {{ arg.name }}
         {%- if arg.is_optional %} = {{ arg.dart_default_value }}
-        {%- if loop.last -%}]{%- endif -%}
+        {#- TODO(eseidel): This does not support having both optional and named arguments! -#}
+        {%- if loop.last -%}{{ '}' if arg.is_named else ']' }}{%- endif -%}
         {%- endif -%}
         {%- if not loop.last %}, {% endif %}
     {%- endfor -%}
-{%- endmacro %}
+{%- endmacro -%}
 
+abstract class {{interface_name}} extends {{ parent_interface if parent_interface else 'NativeFieldWrapperClass2' }} {
+    // Constructors
 {# TODO(eseidel): We only ever have one constructor. #}
-{% for constructor in constructors %}
+{%- for constructor in constructors -%}
     static {{interface_name}} _constructor({{ args_macro(constructor.arguments) }}) native "{{interface_name}}_constructorCallback";
     factory {{interface_name}}({{ args_macro(constructor.arguments) }}) => _constructor(
     {%- for arg in constructor.arguments -%}
         {{ arg.name }}{% if not loop.last %}, {% endif %}
     {%- endfor -%}
     );
 {% endfor %}
 
+    // Attributes
 {% for attribute in attributes %}
     {{ attribute.dart_type }} get {{ attribute.name }} native "{{interface_name}}_{{ attribute.name }}_Getter";
 {% if not attribute.is_read_only %}
     void set {{ attribute.name }}({{ attribute.dart_type }} value) native "{{interface_name}}_{{ attribute.name }}_Setter";
 {% endif %}
 {% endfor %}
 
+    // Methods
 {% for method in methods %}
-    {{method.dart_type}} {{method.name}}({{ args_macro(method.arguments)}} ) native "{{interface_name}}_{{ method.name }}_Callback";
+    {{method.dart_type}} {{method.name}}({{ args_macro(method.arguments)}}) native "{{interface_name}}_{{ method.name }}_Callback";
 {% endfor %}
 }