x/net/html/charset: add missing copyright
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/174240043
diff --git a/html/charset/charset.go b/html/charset/charset.go
index cbabefc..b19f83b 100644
--- a/html/charset/charset.go
+++ b/html/charset/charset.go
@@ -1,3 +1,7 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
// Package charset provides common text encodings for HTML documents.
//
// The mapping from encoding labels to encodings is defined at
diff --git a/html/charset/gen.go b/html/charset/gen.go
index 7229b9c..8b76909 100644
--- a/html/charset/gen.go
+++ b/html/charset/gen.go
@@ -1,3 +1,7 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
// +build ignore
package main
