Add support for GCM cipher suites from RFC 7714.

webrtc/base/opensslstreamadapter.cc

Index: webrtc/base/opensslstreamadapter.cc
diff --git a/webrtc/base/opensslstreamadapter.cc b/webrtc/base/opensslstreamadapter.cc
index 4a1dc8082138a3a44d235f71d04544b8411cf9b2..473f0d2f2b985b71b2321cd2f68ebbabfe2fd8fa 100644
--- a/webrtc/base/opensslstreamadapter.cc
+++ b/webrtc/base/opensslstreamadapter.cc
@@ -55,6 +55,8 @@ struct SrtpCipherMapEntry {
 static SrtpCipherMapEntry SrtpCipherMap[] = {
     {"SRTP_AES128_CM_SHA1_80", SRTP_AES128_CM_SHA1_80},
     {"SRTP_AES128_CM_SHA1_32", SRTP_AES128_CM_SHA1_32},
+    {"SRTP_AEAD_AES_128_GCM", SRTP_AEAD_AES_128_GCM},
+    {"SRTP_AEAD_AES_256_GCM", SRTP_AEAD_AES_256_GCM},
     {nullptr, 0}};
 #endif