IDL: Improve CG for attributes with [CachedAttribute]

Source/bindings/scripts/v8_attributes.py

Index: Source/bindings/scripts/v8_attributes.py
diff --git a/Source/bindings/scripts/v8_attributes.py b/Source/bindings/scripts/v8_attributes.py
index ffa2a435b7f4a49c4d5181013c7941d05d238fdb..0b85ff8c7cd4b79f35b7f6f970c9e7fcd682ebe4 100644
--- a/Source/bindings/scripts/v8_attributes.py
+++ b/Source/bindings/scripts/v8_attributes.py
@@ -191,9 +191,11 @@ def getter_context(interface, attribute, context):
             release = idl_type.release
 
     def v8_set_return_value_statement(for_main_world=False):
-        if context['is_keep_alive_for_gc']:
-            return 'v8SetReturnValue(info, wrapper)'
-        return idl_type.v8_set_return_value(cpp_value, extended_attributes=extended_attributes, script_wrappable='impl', release=release, for_main_world=for_main_world)
+        if context['is_keep_alive_for_gc'] or 'CachedAttribute' in extended_attributes:
+            return 'v8SetReturnValue(info, v8Value)'
+        return idl_type.v8_set_return_value(
+            cpp_value, extended_attributes=extended_attributes, script_wrappable='impl',
+            release=release, for_main_world=for_main_world)
 
     context.update({
         'cpp_value': cpp_value,
@@ -204,7 +206,6 @@ def getter_context(interface, attribute, context):
         'v8_set_return_value': v8_set_return_value_statement(),
     })
 
-
 def getter_expression(interface, attribute, context):
     arguments = []
     this_getter_base_name = getter_base_name(interface, attribute, arguments)