Reviewed by Oliver Hunt.

        Bug 21459: REGRESSION (r37324): Safari crashes inside JavaScriptCore while browsing hulu.com
        <https://bugs.webkit.org/show_bug.cgi?id=21459>

        After r37324, an Arguments object does not mark an associated activation
        object. This change was made because Arguments no longer directly used
        the activation object in any way. However, if an activation is torn off,
        then the backing store of Arguments becomes the register array of the
        activation object. Arguments directly marks all of the arguments, but
        the activation object is being collected, which causes its register
        array to be freed and new memory to be allocated in its place.

        Unfortunately, it does not seem possible to reproduce this issue in a
        layout test.

        * kjs/Arguments.cpp:
        (JSC::Arguments::mark):
        * kjs/Arguments.h:
        (JSC::Arguments::setActivation):
        (JSC::Arguments::Arguments):
        (JSC::JSActivation::copyRegisters):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@37450 268f45cc-cd09-0410-ab3c-d52691b4dbfc