Replace Constants.CompletedTask with Task.CompletedTask (#235)

src/Microsoft.AspNetCore.StaticFiles/Constants.cs

@@ -16,14 +16,5 @@ namespace Microsoft.AspNetCore.StaticFiles
         internal const int Status304NotModified = 304;
         internal const int Status412PreconditionFailed = 412;
         internal const int Status416RangeNotSatisfiable = 416;
-
-        internal static readonly Task CompletedTask = CreateCompletedTask();
-
-        private static Task CreateCompletedTask()
-        {
-            var tcs = new TaskCompletionSource<object>();
-            tcs.SetResult(null);
-            return tcs.Task;
-        }
     }
 }

src/Microsoft.AspNetCore.StaticFiles/DefaultFilesMiddleware.cs

@@ -83,7 +83,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                             {
                                 context.Response.StatusCode = 301;
                                 context.Response.Headers[HeaderNames.Location] = context.Request.PathBase + context.Request.Path + "/" + context.Request.QueryString;
-                                return Constants.CompletedTask;
+                                return Task.CompletedTask;
                             }
 
                             // Match found, re-write the url. A later middleware will actually serve the file.

src/Microsoft.AspNetCore.StaticFiles/DirectoryBrowserMiddleware.cs

@@ -91,7 +91,7 @@ namespace Microsoft.AspNetCore.StaticFiles
                 {
                     context.Response.StatusCode = 301;
                     context.Response.Headers[HeaderNames.Location] = context.Request.PathBase + context.Request.Path + "/" + context.Request.QueryString;
-                    return Constants.CompletedTask;
+                    return Task.CompletedTask;
                 }
 
                 return _formatter.GenerateContentAsync(context, contents);

src/Microsoft.AspNetCore.StaticFiles/HtmlDirectoryFormatter.cs

@@ -51,7 +51,7 @@ namespace Microsoft.AspNetCore.StaticFiles
             if (HttpMethods.IsHead(context.Request.Method))
             {
                 // HEAD, no response body
-                return Constants.CompletedTask;
+                return Task.CompletedTask;
             }
 
             PathString requestPath = context.Request.PathBase + context.Request.Path;

src/Microsoft.AspNetCore.StaticFiles/StaticFileContext.cs

@@ -313,7 +313,7 @@ namespace Microsoft.AspNetCore.StaticFiles
             ApplyResponseHeaders(statusCode);
 
             _logger.LogHandled(statusCode, SubPath);
-            return Constants.CompletedTask;
+            return Task.CompletedTask;
         }
 
         public async Task SendAsync()