Ensure an `ObjectPoolProvider` is registered

- e.g. take advantage of aspnet/HttpAbstractions#561 fix wherever cookies are used

src/Microsoft.AspNetCore.Hosting/WebHostBuilder.cs

@@ -17,6 +17,7 @@ using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.ObjectPool;
 using Microsoft.Extensions.PlatformAbstractions;
 
 namespace Microsoft.AspNetCore.Hosting
@@ -135,7 +136,7 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         /// <summary>
-        /// Configure the provided <see cref="ILoggerFactory"/> which will be available as a hosting service. 
+        /// Configure the provided <see cref="ILoggerFactory"/> which will be available as a hosting service.
         /// </summary>
         /// <param name="configureLogging">The delegate that configures the <see cref="ILoggerFactory"/>.</param>
         /// <returns>The <see cref="IWebHostBuilder"/>.</returns>
@@ -155,7 +156,7 @@ namespace Microsoft.AspNetCore.Hosting
 
             var appEnvironment = hostingContainer.GetRequiredService<IApplicationEnvironment>();
             var startupLoader = hostingContainer.GetRequiredService<IStartupLoader>();
-            
+
             var contentRootPath = ResolveContentRootPath(_options.ContentRootPath, appEnvironment.ApplicationBasePath);
             var applicationName = ResolveApplicationName() ?? appEnvironment.ApplicationName;
 
@@ -201,6 +202,9 @@ namespace Microsoft.AspNetCore.Hosting
             // Conjure up a RequestServices
             services.AddTransient<IStartupFilter, AutoRequestServicesStartupFilter>();
 
+            // Ensure object pooling is available everywhere.
+            services.TryAddSingleton<ObjectPoolProvider, DefaultObjectPoolProvider>();
+
             var defaultPlatformServices = PlatformServices.Default;
             if (defaultPlatformServices.Application != null)
             {

test/Microsoft.AspNetCore.Hosting.Tests/WebHostBuilderTests.cs

@@ -13,8 +13,8 @@ using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Http.Internal;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.ObjectPool;
 using Microsoft.Extensions.PlatformAbstractions;
-using System.Reflection;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Hosting
@@ -92,12 +92,29 @@ namespace Microsoft.AspNetCore.Hosting
             using (host)
             {
                 host.Start();
-                var service = host.Services.GetServices<IApplicationLifetime>();
+                var services = host.Services.GetServices<IApplicationLifetime>();
-                Assert.NotNull(service);
+                Assert.NotNull(services);
+                Assert.NotEmpty(services);
+
                 await AssertResponseContains(server.RequestDelegate, "Exception from constructor");
             }
         }
 
+        [Fact]
+        public void DefaultObjectPoolProvider_IsRegistered()
+        {
+            var server = new TestServer();
+            var host = CreateWebHostBuilder()
+                .UseServer(server)
+                .Configure(app => { })
+                .Build();
+            using (host)
+            {
+                host.Start();
+                Assert.IsType<DefaultObjectPoolProvider>(host.Services.GetService<ObjectPoolProvider>());
+            }
+        }
+
         [Fact]
         public async Task StartupConfigureServicesThrows_Fallback()
         {
@@ -333,7 +350,7 @@ namespace Microsoft.AspNetCore.Hosting
         [Fact]
         public void RelativeContentRootIsResolved()
         {
-            var contentRootNet451 = PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows ? 
+            var contentRootNet451 = PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows ?
                 "testroot" : "../../../../test/Microsoft.AspNetCore.Hosting.Tests/testroot";
 
             var host = new WebHostBuilder()