Store the root object in a hash set, keyed by the plugin view. This is in preparation for 
        letting plugins invalidate the root object upon destruction

        * page/Frame.cpp:
        (WebCore::Frame::createRootObject):
        (WebCore::Frame::cleanupScriptObjects):
        * page/FramePrivate.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@22071 268f45cc-cd09-0410-ab3c-d52691b4dbfc