Reviewed by Sam Weinig.

        A little more encapsulation for MarkedBlock: Made all constants private
        so clients don't know whether allocations are fixed-sized or not
        https://bugs.webkit.org/show_bug.cgi?id=54270
        
        SunSpider reports no change.

        * runtime/CollectorHeapIterator.h:
        (JSC::CollectorHeapIterator::advance): Updated for removal of HeapConstants.

        * runtime/Error.cpp: Switched to using ASSERT_CLASS_FITS_IN_CELL, like
        all other classes.

        * runtime/Heap.cpp:
        (JSC::Heap::allocate): Updated for removal of HeapConstants.
        (JSC::Heap::reset): Updated to use size(), instead of calculating size
        on our own.

        * runtime/Heap.h: Moved the ASSERT here to MarkedBlock, since it enforces
        on special knowledge of fixed-sizery, which only MarkedBlock is supposed
        to know about.

        * runtime/JSCell.h:
        (JSC::JSCell::MarkedBlock::allocate): Updated for removal of HeapConstants.
        Also changed to reset nextCell to 0 at the end of a block, since that
        seems more consistent.

        * runtime/JSGlobalData.cpp:
        (JSC::JSGlobalData::storeVPtrs): Changed to use a fixed array of char.
        This hard-coded size is a little wonky, but the compiler will tell us
        if it's ever wrong, so I think it's OK.

        * runtime/MarkedBlock.cpp:
        (JSC::MarkedBlock::destroy):
        (JSC::MarkedBlock::MarkedBlock):
        (JSC::MarkedBlock::sweep): Updated for removal of HeapConstants.

        * runtime/MarkedBlock.h:
        (JSC::MarkedBlock::isEmpty):
        (JSC::MarkedBlock::clearMarks):
        (JSC::MarkedBlock::size):
        (JSC::MarkedBlock::capacity): Made constants private to this class.
        Removed HeapConstants. Added size() and capacity() functions.

        * runtime/MarkedSpace.cpp:
        (JSC::MarkedSpace::allocate):
        (JSC::MarkedSpace::objectCount):
        (JSC::MarkedSpace::size):
        (JSC::MarkedSpace::capacity):
        * runtime/MarkedSpace.h: Use MarkedBlock helper functions instead of
        direct knowledge of MarkedBlock internals.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@78312 268f45cc-cd09-0410-ab3c-d52691b4dbfc