Change m_contextMenu to an OwnPtr.

        * WebCore.xcodeproj/project.pbxproj:
        * page/ContextMenuController.cpp:
        (WebCore::ContextMenuController::handleContextMenuEvent):
        * page/ContextMenuController.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@17806 268f45cc-cd09-0410-ab3c-d52691b4dbfc