Canvas2D Performance: fix the bottleneck of hasInstance during JS binding -- overloading

Source/bindings/scripts/v8_types.py

Index: Source/bindings/scripts/v8_types.py
diff --git a/Source/bindings/scripts/v8_types.py b/Source/bindings/scripts/v8_types.py
index a63a39326c34290d437e66f575a8979d8e177ec1..e214a39257edacc98fa3a95d5677fb8b0a863ada 100644
--- a/Source/bindings/scripts/v8_types.py
+++ b/Source/bindings/scripts/v8_types.py
@@ -534,7 +534,7 @@ def v8_value_to_cpp_value(idl_type, extended_attributes, v8_value, index, isolat
         cpp_expression_format = 'V8{idl_type}::toImpl({isolate}, {v8_value}, exceptionState)'
     else:
         cpp_expression_format = (
-            'V8{idl_type}::toImplWithTypeCheck({isolate}, {v8_value})')
+            'V8{idl_type}::toImpl(v8::Handle<v8::Object>::Cast({v8_value}))')

[Jens Widell, 2014/09/29 10:04:46]

So what you did here is remove the only type-check for a whole lot of arguments.
That's not a valid change.

This is only valid if the argument was already type-checked because of
[TypeChecking=Interface] *or* if the argument took part in overload resolution
(and was thus type-checked by the overload resolution function.)

And even then, it's also sometimes possible for the argument to be null or
undefined, in which case the cast here is still invalid.

 
     return cpp_expression_format.format(arguments=arguments, idl_type=base_idl_type, v8_value=v8_value, isolate=isolate)