Reviewed by Yury Semikhatsky.

        Web Inspector: enable resource agent upon request.
        https://bugs.webkit.org/show_bug.cgi?id=52815

        We should not send network-related notifications unless front-end
        is interested.

        * inspector/Inspector.idl:
        * inspector/InspectorController.cpp:
        (WebCore::InspectorController::restoreInspectorStateFromCookie):
        (WebCore::InspectorController::connectFrontend):
        (WebCore::InspectorController::resourceAgent):
        * inspector/InspectorController.h:
        (WebCore::InspectorController::consoleAgent):
        (WebCore::InspectorController::cssAgent):
        (WebCore::InspectorController::domAgent):
        (WebCore::InspectorController::injectedScriptAgent):
        (WebCore::InspectorController::runtimeAgent):
        (WebCore::InspectorController::databaseAgent):
        (WebCore::InspectorController::domStorageAgent):
        (WebCore::InspectorController::fileSystemAgent):
        * inspector/InspectorInstrumentation.cpp:
        (WebCore::InspectorInstrumentation::retrieveResourceAgent):
        * inspector/InspectorResourceAgent.cpp:
        (WebCore::InspectorResourceAgent::restore):
        (WebCore::InspectorResourceAgent::~InspectorResourceAgent):
        (WebCore::InspectorResourceAgent::InspectorResourceAgent):
        * inspector/InspectorResourceAgent.h:
        (WebCore::InspectorResourceAgent::create):
        * inspector/InspectorState.cpp:
        (WebCore::InspectorState::InspectorState):
        * inspector/InspectorState.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76249 268f45cc-cd09-0410-ab3c-d52691b4dbfc