godoc/static: mimic the pre-1.10 behavior of strconv.Quote

Thanks to iant for identifying the root cause.

Tested with go1.9 and go1.10.

Fixes golang/go#25880

Change-Id: Ibc3a2aadd92c1e512cf6c537134ee085398e8e6c
Reviewed-on: https://go-review.googlesource.com/118955
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

godoc/static/gen.go

@@ -88,7 +88,15 @@ func Generate() ([]byte, error) {
 		fmt.Fprintf(buf, ",\n\n")
 	}
 	fmt.Fprintln(buf, "}")
-	return format.Source(buf.Bytes())
+
+	b := buf.Bytes()
+
+	// The 鿥 U+9FE5 character became printable in go 1.10,
+	// causing it to appear literally in newer output.
+	// Force the old behavior.
+	b = bytes.Replace(b, []byte("\u9fe5"), []byte(`\u9fe5`), -1)
+
+	return format.Source(b)
 }
 
 // sanitize prepares a valid UTF-8 string as a raw string constant.

godoc/static/gen_test.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build go1.10
-
 package static
 
 import (