IDL: Add support for [Unscopeable] on attributes and methods

Source/bindings/templates/partial_interface.h

 {% include 'copyright_block.txt' %}
 #ifndef {{v8_class_or_partial}}_h
 #define {{v8_class_or_partial}}_h
 
 {% for filename in header_includes %}
 #include "{{filename}}"
 {% endfor %}
 
 namespace blink {
 
@@ skipping 11 matching lines @@
     static void {{attribute.name}}AttributeGetterCustom(const v8::PropertyCallbackInfo<v8::Value>&);
     {% endfilter %}
     {% endif %}
     {% if attribute.has_custom_setter %}{# FIXME: and not attribute.implemented_by #}
     {% filter conditional(attribute.conditional_string) %}
     static void {{attribute.name}}AttributeSetterCustom(v8::Local<v8::Value>, const v8::PropertyCallbackInfo<void>&);
     {% endfilter %}
     {% endif %}
     {% endfor %}
     {# Custom internal fields #}
-    static void installConditionallyEnabledMethods(v8::Local<v8::Object>, v8::Isolate*);
+    static void preparePrototypeObject(v8::Isolate*, v8::Local<v8::Object>);
 private:
     static void install{{v8_class}}Template(v8::Local<v8::FunctionTemplate>, v8::Isolate*);
 };
 }
 #endif // {{v8_class_or_partial}}_h