[Qt] Implement GCActivityCallback
https://bugs.webkit.org/show_bug.cgi?id=103998

Reviewed by Simon Hausmann.

Source/JavaScriptCore:

Implements the activity triggered garbage collector.

* runtime/GCActivityCallback.cpp:
(JSC::DefaultGCActivityCallback::DefaultGCActivityCallback):
(JSC::DefaultGCActivityCallback::scheduleTimer):
(JSC::DefaultGCActivityCallback::cancelTimer):
* runtime/GCActivityCallback.h:
(GCActivityCallback):
(DefaultGCActivityCallback):

Source/WebCore:

Implements the activity triggered garbage collector,
and disables the timer based fallback.

* bindings/js/GCController.cpp:
(WebCore::GCController::GCController):
(WebCore::GCController::garbageCollectSoon):
* bindings/js/GCController.h:
(GCController):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141114 268f45cc-cd09-0410-ab3c-d52691b4dbfc