Handle case where UDP packet contains multiple DTLS records.

webrtc/p2p/base/dtlstransportchannel_unittest.cc

Index: webrtc/p2p/base/dtlstransportchannel_unittest.cc
diff --git a/webrtc/p2p/base/dtlstransportchannel_unittest.cc b/webrtc/p2p/base/dtlstransportchannel_unittest.cc
index 4286d76be33bc37a9b7f694f31b93f79b348e64b..a8ac98775cc4a92c96bb08f961f6f77ab350257c 100644
--- a/webrtc/p2p/base/dtlstransportchannel_unittest.cc
+++ b/webrtc/p2p/base/dtlstransportchannel_unittest.cc
@@ -670,6 +670,22 @@ TEST_F(DtlsTransportChannelTest, TestTransferDtlsTwoChannels) {
   TestTransfer(1, 1000, 100, false);
 }
 
+// Connect with DTLS, combine multiple DTLS records into one packet.
+// Our DTLS implementation doesn't do this, but other implementations may;
+// see https://tools.ietf.org/html/rfc6347#section-4.1.1.
+// This has caused interoperability problems with ORTCLib in the past.
+TEST_F(DtlsTransportChannelTest, TestTransferDtlsCombineRecords) {
+  PrepareDtls(true, true, rtc::KT_DEFAULT);
+  ASSERT_TRUE(Connect());
+  // Our DTLS implementation always sends one record per packet, so to simulate
+  // an endpoint that sends multiple records per packet, we configure the fake
+  // ICE transport to combine every two consecutive packets into a single
+  // packet.
+  cricket::FakeIceTransport* transport = client1_.GetFakeIceTransort(0);
+  transport->combine_outgoing_packets(true);
+  TestTransfer(0, 500, 100, false);
+}
+
 // Connect with A doing DTLS and B not, and transfer some data.
 TEST_F(DtlsTransportChannelTest, TestTransferDtlsRejected) {
   PrepareDtls(true, false, rtc::KT_DEFAULT);