Add tests for the point format extension.

Upstream accidentally started rejecting server-sent point formats in
https://github.com/openssl/openssl/issues/2133. Our own test coverage
here is also lacking, so flesh it out.

Change-Id: I99059558bd28d3a540c9687649d6db7e16579d29
Reviewed-on: https://boringssl-review.googlesource.com/12979
Reviewed-by: Steven Valdez <svaldez@google.com>
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 dd185ce..e527185 100644
--- a/ssl/test/runner/common.go
+++ b/ssl/test/runner/common.go
@@ -127,7 +127,8 @@
 // TLS Elliptic Curve Point Formats
 // http://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-9
 const (
-	pointFormatUncompressed uint8 = 0
+	pointFormatUncompressed    uint8 = 0
+	pointFormatCompressedPrime uint8 = 1
 )
 
 // TLS CertificateStatusType (RFC 3546)
@@ -1238,6 +1239,11 @@
 	// ClearShortHeaderBit, if true, causes the server to send short headers
 	// without the high bit set.
 	ClearShortHeaderBit bool
+
+	// SendSupportedPointFormats, if not nil, is the list of supported point
+	// formats to send in ClientHello or ServerHello. If set to a non-nil
+	// empty slice, no extension will be sent.
+	SendSupportedPointFormats []byte
 }
 
 func (c *Config) serverInit() {