Add support for GCM cipher suites from RFC 7714.

webrtc/p2p/base/transport.h

Index: webrtc/p2p/base/transport.h
diff --git a/webrtc/p2p/base/transport.h b/webrtc/p2p/base/transport.h
index 6b4b37d4c56b89e0abc9617ff58b1fc92d96170e..69ffce71934822639572a1b0f786335450efbd0e 100644
--- a/webrtc/p2p/base/transport.h
+++ b/webrtc/p2p/base/transport.h
@@ -250,6 +250,11 @@ class Transport : public sigslot::has_slots<> {
     return false;
   }
 
+  // Must be called before channel is starting to connect.
+  virtual bool SetEnableGcmCiphers(bool enable) {
+    return false;
+  }
+
  protected:
   // These are called by Create/DestroyChannel above in order to create or
   // destroy the appropriate type of channel.