Cache a ClientHello received before the DTLS handshake has started.

webrtc/p2p/base/dtlstransportchannel.h

Index: webrtc/p2p/base/dtlstransportchannel.h
diff --git a/webrtc/p2p/base/dtlstransportchannel.h b/webrtc/p2p/base/dtlstransportchannel.h
index b6c3cfd2510fba04b20e62c340d0c0fe79d4c59c..f1d4722a34b903c34bdeadf93d28732130345d2d 100644
--- a/webrtc/p2p/base/dtlstransportchannel.h
+++ b/webrtc/p2p/base/dtlstransportchannel.h
@@ -236,6 +236,12 @@ class DtlsTransportChannelWrapper : public TransportChannelImpl {
   rtc::Buffer remote_fingerprint_value_;
   std::string remote_fingerprint_algorithm_;
 
+  // Cached DTLS ClientHello packet that was received before we started the
+  // DTLS handshake. This could happen if the hello was received before the
+  // transport channel became writable, or before a remote fingerprint was
+  // received.
+  rtc::Buffer cached_client_hello_;
+
   RTC_DISALLOW_COPY_AND_ASSIGN(DtlsTransportChannelWrapper);
 };