DTLS-SRTP set up is bypassed when the channel has been writable.

talk/session/media/srtpfilter.cc

Index: talk/session/media/srtpfilter.cc
diff --git a/talk/session/media/srtpfilter.cc b/talk/session/media/srtpfilter.cc
index 4a54740cef2be0433e8f0fda07344f7a49667409..7961a7ba06de370ddd822e03a53f9b1f000fc39b 100644
--- a/talk/session/media/srtpfilter.cc
+++ b/talk/session/media/srtpfilter.cc
@@ -450,6 +450,10 @@ bool SrtpFilter::ApplyParams(const CryptoParams& send_params,
 bool SrtpFilter::ResetParams() {
   offer_params_.clear();
   state_ = ST_INIT;
+  (void)send_session_.release();
+  (void)recv_session_.release();
+  (void)send_rtcp_session_.release();
+  (void)recv_rtcp_session_.release();
   LOG(LS_INFO) << "SRTP reset to init state";
   return true;
 }