Split up Blocks and Media folder roots in Optimizely (Episerver)

InterceptorInit.cs

using EPiServer.Cms.Shell.UI.UIDescriptors;
using EPiServer.Framework;
using EPiServer.Framework.Initialization;
using EPiServer.ServiceLocation;
using EPiServer.ServiceLocation.Compatibility;
using EPiServer.Shell;
using System;
using System.Linq;

namespace ExperimentSite.Widgets
{
    [InitializableModule]
    [ModuleDependency(typeof(EPiServer.Web.InitializationModule))]
    public class InterceptorInit : IConfigurableModule
    {
        public void ConfigureContainer(ServiceConfigurationContext context)
        {
            //Override / remove
            context.Services.Intercept<IContentRepositoryDescriptor>(
                (locator, def) => (def is BlockRepositoryDescriptor) ?
                    locator.GetInstance<MyBlockRepositoryDescriptor>() :
                    (def is MediaRepositoryDescriptor) ? locator.GetInstance<MyMediaRepositoryDescriptor>() : def
                    );

        }

        public void Initialize(InitializationEngine context)
        {
            //Add initialization logic, this method is called once after CMS has been initialized
        }


        public void Uninitialize(InitializationEngine context)
        {
            //Add uninitialization logic
        }
    }
}

RepositoryDescriptors.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using EPiServer;
using EPiServer.Cms.Shell.UI.CompositeViews.Internal;
using EPiServer.Cms.Shell.UI.UIDescriptors;
using EPiServer.Core;
using EPiServer.Framework.Localization;
using EPiServer.ServiceLocation;
using EPiServer.Shell;
using EPiServer.Web;


namespace ExperimentSite.Widgets
{
  public class MyBlockRepositoryDescriptor : BlockRepositoryDescriptor
    {
        private const string NAME = "Blocks";
        private readonly IContentRepository _repo;

        private ContentReference _root;

        public MyBlockRepositoryDescriptor(IContentRepository repo)
        {
            _repo = repo;

            //Get or create root
            ContentFolder rootfolder = _repo.GetChildren<ContentFolder>(ContentReference.GlobalBlockFolder).Where(f => f.Name == NAME).FirstOrDefault();
            if (rootfolder == null)
            {
                rootfolder = _repo.GetDefault<ContentFolder>(ContentReference.GlobalBlockFolder);
                rootfolder.Name = NAME;
                _root = _repo.Save(rootfolder, EPiServer.DataAccess.SaveAction.Publish, EPiServer.Security.AccessLevel.NoAccess);
            }
            else _root = rootfolder.ContentLink;
        }

        public override IEnumerable<ContentReference> Roots
        {
            get
            {
                yield return _root;
            }
        }

    }


    public class MyMediaRepositoryDescriptor : MediaRepositoryDescriptor
    {
        private const string NAME = "Media";
        private readonly IContentRepository _repo;
        private ContentReference _root;

        public MyMediaRepositoryDescriptor(IContentRepository repo)
        {
            _repo = repo;

            //Get or create root
            ContentFolder rootfolder = _repo.GetChildren<ContentFolder>(ContentReference.GlobalBlockFolder).Where(f => f.Name == NAME).FirstOrDefault();
            if (rootfolder == null)
            {
                rootfolder = _repo.GetDefault<ContentFolder>(ContentReference.GlobalBlockFolder);
                rootfolder.Name = NAME;
                _root = _repo.Save(rootfolder, EPiServer.DataAccess.SaveAction.Publish, EPiServer.Security.AccessLevel.NoAccess);
            }
            else _root = rootfolder.ContentLink;
        }
        public override IEnumerable<ContentReference> Roots
        {
            get
            {
                yield return _root;
            }
        }

    }
}