IDL: Remove holder lookup in attribute_getter macro

Source/bindings/templates/attributes.cpp

 {##############################################################################}
 {% macro attribute_getter(attribute, world_suffix) %}
 {% filter conditional(attribute.conditional_string) %}
 static void {{attribute.name}}AttributeGetter{{world_suffix}}(
 {%- if attribute.is_expose_js_accessors %}
 const v8::FunctionCallbackInfo<v8::Value>& info
 {%- else %}
 const v8::PropertyCallbackInfo<v8::Value>& info
 {%- endif %})
 {
     {% if attribute.is_reflect and not attribute.is_url and
           attribute.idl_type == 'DOMString' and is_node %}
     {% set cpp_class, v8_class = 'Element', 'V8Element' %}
     {% endif %}
     {# holder #}
-    {% if attribute.is_unforgeable and interface_name != 'Window' %}
-    {# perform lookup first #}
-    {# FIXME: can we remove this lookup? #}
-    v8::Handle<v8::Object> holder = {{v8_class}}::findInstanceInPrototypeChain(info.This(), info.GetIsolate());
-    if (holder.IsEmpty())
-        return;
-    {% elif not attribute.is_static %}
+    {% if not attribute.is_static %}
     v8::Handle<v8::Object> holder = info.Holder();
     {% endif %}
     {# impl #}
     {% if attribute.cached_attribute_validation_method %}
     v8::Handle<v8::String> propertyName = v8AtomicString(info.GetIsolate(), "{{attribute.name}}");
     {{cpp_class}}* impl = {{v8_class}}::toNative(holder);
     if (!impl->{{attribute.cached_attribute_validation_method}}()) {
         v8::Handle<v8::Value> v8Value = V8HiddenValue::getHiddenValue(info.GetIsolate(), holder, propertyName);
         if (!v8Value.IsEmpty()) {
             v8SetReturnValue(info, v8Value);
@@ skipping 311 matching lines @@
     {% endif %}
     {% if attribute.has_custom_setter %}
     {{v8_class}}::{{attribute.name}}AttributeSetterCustom(v8Value, info);
     {% else %}
     {{cpp_class}}V8Internal::{{attribute.name}}AttributeSetter{{world_suffix}}(v8Value, info);
     {% endif %}
     TRACE_EVENT_SET_SAMPLING_STATE("v8", "V8Execution");
 }
 {% endfilter %}
 {% endmacro %}