The answer to it is HttpContext.Current.Items
I'm planning to use HttpContext.Current.Items for preserving pointers to controls that would render final javascript on the pages.
Or may be preserve javascript itself and then make these controls to retrieve the javascript from HttpContext.Current.Items["BottomScriptBuilder"] and HttpContext.Current.Items["HeadScriptBuilder"]?
System.Web.HttpContext.Current.Items is actually pretty old thing in ASP.NET
