[V8] Call Isolate::GetCurrent() in a callback from WebCore
https://bugs.webkit.org/show_bug.cgi?id=106766

Reviewed by Adam Barth.

The objective is to pass an Isolate everywhere.
Given that a callback from WebCore is an entry point to V8,
we can call Isolate::GetCurrent() at the head of the callback
and pass it to other places. (In practice, handleEvent() is
the only callback used in the current WebKit.)

No tests. No change in behavior.

* bindings/scripts/CodeGeneratorV8.pm:
(GenerateCallbackImplementation):
(NativeToJSValue):
* bindings/scripts/test/V8/V8TestCallback.cpp:
(WebCore::V8TestCallback::callbackWithNoParam):
(WebCore::V8TestCallback::callbackWithClass1Param):
(WebCore::V8TestCallback::callbackWithClass2Param):
(WebCore::V8TestCallback::callbackWithStringList):
(WebCore::V8TestCallback::callbackWithBoolean):
(WebCore::V8TestCallback::callbackRequiresThisToPass):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@139599 268f45cc-cd09-0410-ab3c-d52691b4dbfc