Reviewed by Timothy.

    Reviewed by Timothy.

        http://bugzilla.opendarwin.org/show_bug.cgi?id=6635
        Bug 6635: Crash selecting inspector nodes for tabs that aren't foremost

        Stop observing window will close notifications before we tell the highlight window to close,
        this prevents the crash. Also prevent drawing highlights for hidden tabs.

        * WebInspector/WebInspector.m:
        (-[WebInspector _highlightNode:]):
        * WebInspector/WebNodeHighlight.m:
        (-[WebNodeHighlight expire]):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@13978 268f45cc-cd09-0410-ab3c-d52691b4dbfc