Replace PlatformAbstractions with RuntimeInformation

Author: BrennanConroy

test/Microsoft.AspNetCore.StaticFiles.Tests/StaticFilesTestServer.cs

@@ -3,20 +3,20 @@
 
 using System;
 using System.Collections.Generic;
+using System.Runtime.InteropServices;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.PlatformAbstractions;
 
 namespace Microsoft.AspNetCore.StaticFiles
 {
     public static class StaticFilesTestServer
     {
         public static TestServer Create(Action<IApplicationBuilder> configureApp, Action<IServiceCollection> configureServices = null)
         {
-            var contentRootNet451 = PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows ?
+            var contentRootNet451 = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ?
                 "." : "../../../../test/Microsoft.AspNetCore.StaticFiles.Tests";
             Action<IServiceCollection> defaultConfigureServices = services => { };
             var configuration = new ConfigurationBuilder()

test/Microsoft.AspNetCore.StaticFiles.Tests/project.json

@@ -16,6 +16,7 @@
     ]
   },
   "dependencies": {
+    "System.Runtime.InteropServices.RuntimeInformation": "4.0.0-*",
     "dotnet-test-xunit": "1.0.0-*",
     "Microsoft.NETCore.Platforms": "1.0.1-*",
     "Microsoft.AspNetCore.StaticFiles": "1.0.0-*",