[bindings] Support is_explicit_nullable for method arguments.

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 a06d29fffe7e5052dbd875a753b17541839bcfd2..e7468be786364ff0f2b81b71b8929a9368fc8d94 100644
--- a/Source/bindings/templates/methods.cpp
+++ b/Source/bindings/templates/methods.cpp
@@ -178,6 +178,10 @@ if (!isUndefinedOrNull(info[{{argument.index}}]) && !info[{{argument.index}}]->I
 }
 {% endif %}{# not argument.use_permissive_dictionary_conversion #}
 {{v8_value_to_local_cpp_value(argument)}}
+{% elif argument.is_explicit_nullable %}
+if (!info[{{argument.index}}]->IsNull()) {

[Jens Widell, 2015/03/02 11:04:35]

The check here should be

  if (!isUndefinedOrNull(info[{{argument.index}}])) {

(I realize I suggested using IsNull() earlier; I was mistaken then. Web IDL
actually says to treat both ECMAScript null and undefined as "IDL null".)

+    {{v8_value_to_local_cpp_value(argument) | indent}}
+}
 {% else %}{# argument.is_nullable #}
 {{v8_value_to_local_cpp_value(argument)}}
 {% endif %}{# argument.is_nullable #}