There were at least two ways you could get the highlight to appear
        when it shouldn't:
          1) Selecting a node in the Inspector while the inspected WebView was
             in a background tab.
          2) Selecting a node in the Inspector, switching to another tab,
             closing the Inspector, then switching back to the inspected
             WebView's tab.

        This patch fixes the above two issues, and possibly others.

        show() and hide() are now private methods of WebNodeHighlight. They
        are replaced by a single public method,
        setShowsWhileWebViewIsVisible(bool). WebInspectorClient uses this to
        tell the highlight whether it should be showing when the inspected
        WebView is visible.

        Reviewed by John Sullivan.

        * WebCoreSupport/WebInspectorClient.cpp:
        (WebInspectorClient::highlight): If the highlight is already showing,
        it just needs to update since the highlighted node has changed. If the
        highlight is not showing, call setShowsWhileWebViewIsVisible(true) so
        that the highlight will show when the WebView is shown.
        (WebInspectorClient::hideHighlight): Changed to call
        setShowsWhileWebViewIsVisible(false) instead of hide().
        * WebNodeHighlight.cpp:
        (WebNodeHighlight::WebNodeHighlight): Initialize new member, and
        initialize m_inspectedWebViewWindow to its final value here instead of
        in show().
        (WebNodeHighlight::setShowsWhileWebViewIsVisible): Added. If we're not
        supposed to show ourselves when the WebView is visible, we hide
        ourselves and return. Otherwise, we make our visibility match the
        WebView's.
        (WebNodeHighlight::isWebViewVisible): Added.
        (WebNodeHighlight::show): Removed initialization of
        m_inspectedWebViewWindow (this is now done by our constructor). Added
        an assertion that we're supposed to show ourselves when the WebView is
        visible.
        (WebNodeHighlight::onWebViewShowWindow): If we shouldn't show
        ourselves when the WebView is visible, then we don't need to do
        anything at all when the WebView's visibility changes.
        * WebNodeHighlight.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@31164 268f45cc-cd09-0410-ab3c-d52691b4dbfc