GitLab

This CL introduces:
 - ThreadState::registerPreFinalizer(T&)
 - ThreadState::unregisterPreFinalizer(T&)
 - USING_PRE_FINALIZER(Class, method)

They are used like the following:

class Foo : GarbageCollected<Foo> {
    USING_PRE_FINALIZER(Foo, dispose);
public:
    Foo() { ThreadState::current()->registerPreFinalizer(*this); }
    void trace(Visitor*);
    ...
private:
    void dispose();

    Member<Bar> m_bar;
};

void Foo::dispose()
{
    m_bar->doesSomething();
}


BUG=420515

Review URL: https://codereview.chromium.org/623033002

git-svn-id: svn://svn.chromium.org/blink/trunk@183253 bbb929c8-8fbe-4397-9dbb-9b2b20218538