Added missing copyright header

src/Microsoft.AspNetCore.Server.Kestrel/Internal/Http/Frame.Generated.cs

@@ -1,3 +1,5 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
 using System.Collections.Generic;

src/Microsoft.AspNetCore.Server.Kestrel/Internal/Http/FrameHeaders.Generated.cs

@@ -1,3 +1,5 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
 using System.Collections.Generic;

tools/Microsoft.AspNetCore.Server.Kestrel.GeneratedCode/FrameFeatureCollection.cs

@@ -62,7 +62,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.GeneratedCode
                 typeof(IHttpConnectionFeature)
             };
 
-            return $@"
+            return $@"// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
 using System;
 using System.Collections.Generic;
 

tools/Microsoft.AspNetCore.Server.Kestrel.GeneratedCode/KnownHeaders.cs

@@ -262,7 +262,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.GeneratedCode
                     offset += header.BytesCount;
                 }
             }
-            return $@"
+            return $@"// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
 using System;
 using System.Collections.Generic;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure;