Fix Bug 19051: REGRESSION (r33447): Assertion in JSDebugServer::removeListener closing tab with Inspector open

        m_inspectedPage is now cleared when the Page is destroyed, which never
        used to happen. Some of InspectorController's code was not prepared
        for this.

        Reviewed by Dave Hyatt.

        * page/InspectorController.cpp:
        (WebCore::InspectorController::~InspectorController): Removed a call
        to stopDebugging and added an assertion. Debugging should have already
        been stopped by this point.
        (WebCore::InspectorController::inspectedPageDestroyed): Moved here
        from the header file. Added a call to stopDebugging.
        (WebCore::InspectorController::enabled): Return false if our inspected
        Page has already been destroyed, since we can't really do much at this
        point anyway.
        (WebCore::InspectorController::didCommitLoad):
        (WebCore::InspectorController::didLoadResourceFromMemoryCache):
        (WebCore::InspectorController::identifierForInitialRequest):
        (WebCore::InspectorController::startDebuggingAndReloadInspectedPage):
        (WebCore::InspectorController::stopDebugging):
        (WebCore::InspectorController::drawNodeHighlight):
        Assert that m_inspectedPage hasn't been cleared.
        * page/InspectorController.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@33450 268f45cc-cd09-0410-ab3c-d52691b4dbfc