Add tests around compression methods.

Not that this matters in the slightest, but the recent IETF mailing
reminded me we don't test this.

Change-Id: I300c96d6a63733d538a7019a7cb74d4e65d0498f
Reviewed-on: https://boringssl-review.googlesource.com/10961
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/ssl/test/runner/common.go b/ssl/test/runner/common.go
index e1574d3..c73d74c 100644
--- a/ssl/test/runner/common.go
+++ b/ssl/test/runner/common.go
@@ -1063,6 +1063,10 @@
 	// SendSNIWarningAlert, if true, causes the server to send an
 	// unrecognized_name alert before the ServerHello.
 	SendSNIWarningAlert bool
+
+	// SendCompressionMethods, if not nil, is the compression method list to
+	// send in the ClientHello.
+	SendCompressionMethods []byte
 }
 
 func (c *Config) serverInit() {