Use service provider from StartPagePackage

Author: jcansdale

src/GitHub.VisualStudio.16/ExtensionServicesFactory.cs

@@ -16,6 +16,8 @@ public ExtensionServicesFactory(IServiceProvider serviceProvider)
 
         public IExtensionServices Create()
         {
+            ThreadHelper.ThrowIfNotOnUIThread();
+
             var package = FindGitHubPackage();
             if(package != null)
             {

src/GitHub.VisualStudio.16/StartPagePackage.cs

@@ -20,22 +20,28 @@ namespace GitHub.StartPage
     [ProvideCodeContainerProvider("GitHub Container", Guids.StartPagePackageId, Images.ImageMonikerGuid, Images.Logo, "#110", "#111", typeof(GitHubContainerProvider))]
     public sealed class StartPagePackage : ExtensionPointPackage
     {
+        protected override void Initialize()
+        {
+            base.Initialize();
+            ServiceProvider = this;
+        }
+
+        internal static IServiceProvider ServiceProvider { get; private set; }
     }
 
     [Guid(Guids.CodeContainerProviderId)]
     public class GitHubContainerProvider : ICodeContainerProvider
     {
         readonly ICodeContainerProvider provider;
 
-        public GitHubContainerProvider() : this(null)
+        public GitHubContainerProvider() : this(StartPagePackage.ServiceProvider)
         {
         }
 
         public GitHubContainerProvider(IServiceProvider serviceProvider)
         {
             ThreadHelper.ThrowIfNotOnUIThread();
 
-            serviceProvider = serviceProvider ?? ServiceProvider.GlobalProvider;
             var factory = new ExtensionServicesFactory(serviceProvider);
             var services = factory.Create();
             provider = services.GetGitHubContainerProvider();