Implement ALPN in runner.go.

Imported from upstream's https://codereview.appspot.com/108710046.

Change-Id: I66c879dcc9fd09446ac1a8380f796b1d68c89e4e
Reviewed-on: https://boringssl-review.googlesource.com/1751
Reviewed-by: Adam Langley <agl@google.com>
4 files changed