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 e33041bb0a4df4aa0bb441c9ceda7aa41767648e..85bb19408844248a99a4a1b59a5838013e6c0ebd 100644
--- a/Source/bindings/templates/methods.cpp
+++ b/Source/bindings/templates/methods.cpp
@@ -61,19 +61,23 @@ static void {{method.name}}{{method.overload_index}}Method{{world_suffix}}(const
 {######################################}
 {% 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.is_optional %}
     if (!info[{{argument.index}}]->IsUndefined()) {
         {{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}}
@@ -88,39 +92,24 @@ static void {{method.name}}{{method.overload_index}}Method{{world_suffix}}(const
 {% 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' #}
+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}}{% if argument.is_explicit_optional %}{{argument.cpp_type_initializer}}{% endif %};
+{% 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
-      not argument.is_callback_interface %}
-{# Optional arguments without a default value generate an early call with
-   fewer arguments if they are omitted.
-   Optional Dictionary arguments default to empty dictionary. #}
-if (UNLIKELY(info.Length() <= {{argument.index}})) {
-    {% if world_suffix %}
-    {{cpp_method_call(method, argument.v8_set_return_value_for_main_world, argument.cpp_value) | indent}}
-    {% else %}
-    {{cpp_method_call(method, argument.v8_set_return_value, argument.cpp_value) | indent}}
-    {% endif %}
-    {% if argument.has_event_listener_argument %}
-    {{hidden_dependency_action(method.name) | indent}}
-    {% endif %}
-    return;
-}
-{% endif %}
 {% if argument.has_type_checking_interface and not argument.is_variadic_wrapper_type %}
 {# Type checking for wrapper interface types (if interface not implemented,
    throw a TypeError), per http://www.w3.org/TR/WebIDL/#es-interface