http2: don't make garbage when sorting things

benchmark                        old ns/op     new ns/op     delta
BenchmarkServer_GetRequest-2     259453        256050        -1.31%

benchmark                        old allocs     new allocs     delta
BenchmarkServer_GetRequest-2     24             22             -8.33%

benchmark                        old bytes     new bytes     delta
BenchmarkServer_GetRequest-2     1599          1532          -4.19%

Change-Id: Ieb11a3bd4c752567e0401bcc5e77e027cfb8063c
Reviewed-on: https://go-review.googlesource.com/20999
Reviewed-by: Andrew Gerrand <adg@golang.org>
4 files changed