IDL: make optional arguments (without default) explicit sometimes

Source/bindings/templates/methods.cpp

Index: Source/bindings/templates/methods.cpp
diff --git a/Source/bindings/templates/methods.cpp b/Source/bindings/templates/methods.cpp
index 0650c48664fea7f36890f858e7e8521d162a5d84..af976dc5bc24f457a0a26a4bb6ac785811609af9 100644
--- a/Source/bindings/templates/methods.cpp
+++ b/Source/bindings/templates/methods.cpp
@@ -76,19 +76,23 @@ if (listener && !impl->toNode())
 {######################################}
 {% macro generate_arguments(method, world_suffix) %}
 {% for argument in method.arguments %}
-{{generate_argument_var_declaration(argument)}};
-{% endfor %}
+{{generate_argument_var_declaration(argument)}}
+{%- endfor %}
 {
     {% if method.arguments_need_try_catch %}
     v8::TryCatch block;
     V8RethrowTryCatchScope rethrow(block);
     {% endif %}
     {% for argument in method.arguments %}
-    {% if argument.default_value %}
+    {% if argument.default_value or argument.is_explicit_optional %}
     if (info.Length() > {{argument.index}}) {
         {{generate_argument(method, argument, world_suffix) | indent(8)}}
     } else {
+        {% if argument.default_value %}
         {{argument.name}} = {{argument.default_value}};
+        {% else %}
+        {{argument.name}}Missing = true;
+        {% endif %}
     }
     {% else %}
     {{generate_argument(method, argument, world_suffix) | indent}}
@@ -103,23 +107,26 @@ if (listener && !impl->toNode())
 {% if argument.is_callback_interface %}
 {# FIXME: remove EventListener special case #}
 {% if argument.idl_type == 'EventListener' %}
-RefPtr<{{argument.idl_type}}> {{argument.name}}
-{%- else %}
-OwnPtr<{{argument.idl_type}}> {{argument.name}}
-{%- endif %}{# argument.idl_type == 'EventListener' #}
-{%- elif argument.is_clamp %}{# argument.is_callback_interface #}
+RefPtr<{{argument.idl_type}}> {{argument.name}};
+{% else %}
+OwnPtr<{{argument.idl_type}}> {{argument.name}};
+{% endif %}{# argument.idl_type == 'EventListener' #}
+{% elif argument.is_clamp %}{# argument.is_callback_interface #}
 {# NaN is treated as 0: http://www.w3.org/TR/WebIDL/#es-type-mapping #}
-{{argument.cpp_type}} {{argument.name}} = 0
-{%- else %}
-{{argument.cpp_type}} {{argument.name}}
-{%- endif %}
-{% endmacro %}
+{{argument.cpp_type}} {{argument.name}} = 0;
+{% else %}
+{{argument.cpp_type}} {{argument.name}};
+{% endif %}
+{% if argument.is_explicit_optional %}
+bool {{argument.name}}Missing = false;
+{% endif %}
+{%- endmacro %}
 
 
 {######################################}
 {% macro generate_argument(method, argument, world_suffix) %}
-{% if argument.is_optional and not argument.has_default and
-      argument.idl_type != 'Dictionary' and
+{% if argument.is_optional and not argument.is_explicit_optional and
+      not argument.has_default and argument.idl_type != 'Dictionary' and
       not argument.is_callback_interface %}
 {# Optional arguments without a default value generate an early call with
    fewer arguments if they are omitted.