Fix bug 574524: DtlsTransportChannel crashes after SSL closes remotely

webrtc/p2p/base/dtlstransportchannel.cc

Index: webrtc/p2p/base/dtlstransportchannel.cc
diff --git a/webrtc/p2p/base/dtlstransportchannel.cc b/webrtc/p2p/base/dtlstransportchannel.cc
index e1de4514ff93834a30fe68af2613a0b37433628a..d3e973bd64a23bdad079de8535f04bb051b876be 100644
--- a/webrtc/p2p/base/dtlstransportchannel.cc
+++ b/webrtc/p2p/base/dtlstransportchannel.cc
@@ -88,6 +88,11 @@ bool StreamInterfaceChannel::OnPacketReceived(const char* data, size_t size) {
   return ret;
 }
 
+void StreamInterfaceChannel::Close() {
+  packets_.Clear();
+  state_ = rtc::SS_CLOSED;
+}
+
 DtlsTransportChannelWrapper::DtlsTransportChannelWrapper(
     Transport* transport,
     TransportChannelImpl* channel)