Add header text to proto-gae tool

tools/proto-gae/proto_gae.go

Index: tools/proto-gae/proto_gae.go
diff --git a/tools/proto-gae/proto_gae.go b/tools/proto-gae/proto_gae.go
index 6db06781b3e1ee3ee3bfcb39f3e37d7f40051e2d..7ec4e5a989da7d647ea66269bdac47588dd1f306 100644
--- a/tools/proto-gae/proto_gae.go
+++ b/tools/proto-gae/proto_gae.go
@@ -24,6 +24,7 @@ type app struct {
 	packageName string
 	typeNames   stringsetflag.Flag
 	outFile     string
+	header      string
 }
 
 const help = `Usage of %s:
@@ -40,6 +41,11 @@ methods for the named types.
 Options:
 `
 
+const copyright = `// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+`
+
 func (a *app) parseArgs(fs *flag.FlagSet, args []string) error {
 	fs.SetOutput(a.out)
 	fs.Usage = func() {
@@ -51,6 +57,8 @@ func (a *app) parseArgs(fs *flag.FlagSet, args []string) error {
 		"A generated proto.Message type to generate stubs for (required, repeatable)")
 	fs.StringVar(&a.outFile, "out", "proto_gae.gen.go",
 		"The name of the output file")
+	fs.StringVar(&a.header, "header", copyright, "Header text to put at the top of "+
+		"the generated file. Defaults to the Chromium Authors copyright.")
 
 	if err := fs.Parse(args[1:]); err != nil {
 		return err
@@ -74,7 +82,8 @@ func (a *app) parseArgs(fs *flag.FlagSet, args []string) error {
 }
 
 var tmpl = template.Must(
-	template.New("main").Parse(`// AUTOGENERATED: Do not edit
+	template.New("main").Parse(`{{if index . "header"}}{{index . "header"}}
+{{end}}// AUTOGENERATED: Do not edit
 
 package {{index . "package"}}
 
@@ -115,6 +124,7 @@ func (a *app) writeTo(w io.Writer) error {
 	return tmpl.Execute(w, map[string]interface{}{
 		"package": a.packageName,
 		"types":   typeNames,
+		"header":  a.header,
 	})
 }