Minor fixes as per PR#3852 discussion

src/Umbraco.Web/Runtime/WebRuntimeComponent.cs

@@ -127,12 +127,8 @@ namespace Umbraco.Web.Runtime
             composition.Container.RegisterUmbracoControllers(typeLoader, GetType().Assembly);
             composition.Container.EnableWebApi(GlobalConfiguration.Configuration);
 
-            //we aren't scanning for ISearchableTree since that is not IDiscoverable, instead we'll just filter what we've
-            //already scanned since all of our ISearchableTree is of type UmbracoApiController and in most cases any developers'
-            //own trees they want searched will also be of type UmbracoApiController. If a developer wants to replace one of ours
-            //then they will have to manually register/replace.
             composition.Container.RegisterCollectionBuilder<SearchableTreeCollectionBuilder>()
-                .Add(() => typeLoader.GetTypes<UmbracoApiController>().Where(x => x.Implements<ISearchableTree>()));
+                .Add(() => typeLoader.GetTypes<ISearchableTree>());
 
             composition.Container.Register<UmbracoTreeSearcher>(new PerRequestLifeTime());
 

src/Umbraco.Web/Search/SearchableTreeCollection.cs

@@ -1,6 +1,8 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
+using Umbraco.Core;
 using Umbraco.Core.Composing;
 using Umbraco.Core.Services;
 using Umbraco.Web.Trees;
@@ -22,11 +24,11 @@ namespace Umbraco.Web.Search
             var appTrees = treeService.GetAll()
                 .OrderBy(x => x.SortOrder)
                 .ToArray();
-            var dictionary = new Dictionary<string, SearchableApplicationTree>();
+            var dictionary = new Dictionary<string, SearchableApplicationTree>(StringComparer.OrdinalIgnoreCase);
             var searchableTrees = this.ToArray();
             foreach (var appTree in appTrees)
             {
-                var found = searchableTrees.FirstOrDefault(x => x.TreeAlias == appTree.Alias);
+                var found = searchableTrees.FirstOrDefault(x => x.TreeAlias.InvariantEquals(appTree.Alias));
                 if (found != null)
                 {
                     dictionary[found.TreeAlias] = new SearchableApplicationTree(appTree.ApplicationAlias, appTree.Alias, found);

src/Umbraco.Web/Trees/ISearchableTree.cs

@@ -1,9 +1,10 @@
 using System.Collections.Generic;
+using Umbraco.Core.Composing;
 using Umbraco.Web.Models.ContentEditing;
 
 namespace Umbraco.Web.Trees
 {
-    public interface ISearchableTree
+    public interface ISearchableTree : IDiscoverable
     {
         /// <summary>
         /// The alias of the tree that the <see cref="ISearchableTree"/> belongs to