Reviewed by Adam.

        http://bugzilla.opendarwin.org/show_bug.cgi?id=10838
        Bug 10838: REGRESSION: Leaking of WebScriptObjectPrivate

        FrameMac relies on its cleanupPluginObjects being called to perform cleanup.  The virtual
        Frame::cleanupPluginObjects method is called from Frame's destructor, which results
        in Frame::cleanupPluginObjects being called rather than FrameMac::cleanupPluginObjects.

        * bridge/mac/FrameMac.mm:
        (WebCore::FrameMac::~FrameMac): Call cancelAndClear to ensure that FrameMac::cleanupPluginObjects
        will be called from Frame::clear
        * page/Frame.cpp:
        (WebCore::Frame::~Frame): Use cancelAndClear.
        (WebCore::Frame::cancelAndClear): Move cancellation and clearing into a separate method that
        FrameMac can use.
        * page/Frame.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@16368 268f45cc-cd09-0410-ab3c-d52691b4dbfc