Fixes IPublishedShapshot and friends

src/Umbraco.Web/PublishedCache/XmlPublishedCache/PublishedSnapshot.cs

@@ -0,0 +1,59 @@
+using System;
+using Umbraco.Core;
+using Umbraco.Core.Cache;
+
+namespace Umbraco.Web.PublishedCache.XmlPublishedCache
+{
+    /// <summary>
+    /// Implements a published snapshot.
+    /// </summary>
+    class PublishedSnapshot : IPublishedSnapshot
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="PublishedSnapshot"/> class with a content cache
+        /// and a media cache.
+        /// </summary>
+        public PublishedSnapshot(
+            PublishedContentCache contentCache,
+            PublishedMediaCache mediaCache,
+            PublishedMemberCache memberCache,
+            DomainCache domainCache)
+        {
+            Content = contentCache;
+            Media = mediaCache;
+            Members = memberCache;
+            Domains = domainCache;
+        }
+
+        /// <inheritdoc />
+        public IPublishedContentCache Content { get; }
+
+        /// <inheritdoc />
+        public IPublishedMediaCache Media { get; }
+
+        /// <inheritdoc />
+        public IPublishedMemberCache Members { get; }
+
+        /// <inheritdoc />
+        public IDomainCache Domains { get; }
+
+        /// <inheritdoc />
+        public ICacheProvider SnapshotCache => null;
+
+        /// <inheritdoc />
+        public ICacheProvider ElementsCache => null;
+
+        /// <inheritdoc />
+        public IDisposable ForcedPreview(bool preview, Action<bool> callback = null)
+        {
+            // the XML cache does not support forcing preview, really, so, just pretend...
+            return new ForcedPreviewObject();
+        }
+
+        private class ForcedPreviewObject : DisposableObject
+        {
+            protected override void DisposeResources()
+            { }
+        }
+    }
+}