https://bugs.webkit.org/show_bug.cgi?id=123380

Reviewed by Geoffrey Garen.

Support for constructor-style callbacks for the Objective-C API to JSC is currently limited to 
Objective-C blocks. Any clients who try to call the constructor of a JSExport-ed Objective-C class 
are met with a type error stating that it cannot be called as a constructor.

It would be nice to expand JSExport's functionality to support this idiom. It is a natural 
extension to JSExport and would increase the expressiveness and simplicity in both Objective-C and 
JavaScript client code.

The way we'll do this is to expand the capabilities of ObjCCallbackFunction and associated classes. 
Instead of constructing a normal C API object for the constructor, we'll instead allocate a full-blown 
ObjCCallbackFunction object which can already properly handle being invoked as a constructor.

* API/JSWrapperMap.mm:
(copyMethodsToObject):
(allocateConstructorForCustomClass):
(-[JSObjCClassInfo allocateConstructorAndPrototypeWithSuperClassInfo:]):
(tryUnwrapObjcObject):
* API/ObjCCallbackFunction.h:
(JSC::ObjCCallbackFunction::impl):
* API/ObjCCallbackFunction.mm:
(JSC::ObjCCallbackFunctionImpl::ObjCCallbackFunctionImpl):
(JSC::ObjCCallbackFunctionImpl::wrappedConstructor):
(JSC::ObjCCallbackFunctionImpl::isConstructible):
(JSC::ObjCCallbackFunction::getConstructData):
(JSC::ObjCCallbackFunctionImpl::name):
(JSC::ObjCCallbackFunctionImpl::call):
(objCCallbackFunctionForInvocation):
(objCCallbackFunctionForInit):
(tryUnwrapConstructor):
* API/tests/testapi.mm:
(-[TextXYZ initWithString:]):
(-[ClassA initWithA:]):
(-[ClassB initWithA:b:]):
(-[ClassC initWithA:]):
(-[ClassC initWithA:b:]):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@158286 268f45cc-cd09-0410-ab3c-d52691b4dbfc