Add support for GCM cipher suites from RFC 7714.

talk/app/webrtc/peerconnection.cc

Index: talk/app/webrtc/peerconnection.cc
diff --git a/talk/app/webrtc/peerconnection.cc b/talk/app/webrtc/peerconnection.cc
index 83e29191c8a2ac1b5003e5f684d7755250f11dec..5047555bbd2fad605bc2cb84c0de90f0dc763685 100644
--- a/talk/app/webrtc/peerconnection.cc
+++ b/talk/app/webrtc/peerconnection.cc
@@ -1472,6 +1472,7 @@ bool PeerConnection::GetOptionsForOffer(
   if (session_->data_channel_type() == cricket::DCT_SCTP && HasDataChannels()) {
     session_options->data_channel_type = cricket::DCT_SCTP;
   }
+  session_options->enable_gcm_ciphers = factory_->options().enable_gcm_ciphers;
   return true;
 }
 
@@ -1496,6 +1497,7 @@ bool PeerConnection::GetOptionsForAnswer(
   if (session_->data_channel_type() == cricket::DCT_SCTP) {
     session_options->data_channel_type = cricket::DCT_SCTP;
   }
+  session_options->enable_gcm_ciphers = factory_->options().enable_gcm_ciphers;
   return true;
 }