https://bugs.webkit.org/show_bug.cgi?id=122561

Reviewed by Oliver Hunt.

Currently the only way for clients to vend new native objects to JavaScript code
is via factory methods in the form of exported class methods or blocks. Blocks can
be called like normal functions from JavaScript code, but they cannot be invoked
with 'new'. This would give a simple way for clients to expose constructor-like
behavior to their JavaScript code.

This patch adds the ability for blocks to be invoked as if they were a constructor.
Blocks invoked as constructors are required to return an object. If the block doesn't
return an object then an error is thrown. The 'this' object is not provided to the
block and must be created within the block itself.

This patch also unifies the native 'construct' callback used in both the C and Obj-C
APIs under the APICallbackFunction struct, similar to how we unified the 'call' callback
between ObjCCallbackFunction and JSCallbackFunction before.

This patch also adds tests to make sure that different blocks generate objects that
correctly behave when queried with instanceof. It also makes sure that the correct
JS exception is thrown when a block fails to return an object.

* API/APICallbackFunction.h:
(JSC::APICallbackFunction::call):
(JSC::APICallbackFunction::construct):
* API/JSCallbackConstructor.cpp:
(JSC::JSCallbackConstructor::getConstructData):
* API/JSCallbackConstructor.h:
(JSC::JSCallbackConstructor::constructCallback):
* API/JSCallbackFunction.h:
(JSC::JSCallbackFunction::functionCallback):
* API/ObjCCallbackFunction.h:
(JSC::ObjCCallbackFunction::functionCallback):
(JSC::ObjCCallbackFunction::constructCallback):
* API/ObjCCallbackFunction.mm:
(JSC::objCCallbackFunctionCallAsConstructor):
(JSC::ObjCCallbackFunction::ObjCCallbackFunction):
(JSC::ObjCCallbackFunction::create):
(JSC::ObjCCallbackFunction::getConstructData):
* API/tests/testapi.mm:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157234 268f45cc-cd09-0410-ab3c-d52691b4dbfc