Revert "Replace BundleFilter with RtpDemuxer in RtpTransport."

This reverts commit ea8b62a3e74fe91cd6bf66304839cd5677880a4e.

Reason for revert: Broke chromium tests.
Original change's description:
> Replace BundleFilter with RtpDemuxer in RtpTransport.
> 
> BundleFilter is replaced by RtpDemuxer in RtpTransport for payload
> type-based demuxing. RtpTransport will support MID-based demuxing later.
> 
> Each BaseChannel has its own RTP demuxing criteria and when connecting
> to the RtpTransport, BaseChannel will register itself as a demuxer sink.
> 
> The inheritance model is changed. New inheritance chain:
> DtlsSrtpTransport->SrtpTransport->RtpTranpsort
> 
> NOTE:
> When RTCP packets are received, Call::DeliverRtcp will be called for
> multiple times (webrtc:9035) which is an existing issue. With this CL,
> it will become more of a problem and should be fixed.
> 
> Bug: webrtc:8587
> Change-Id: I1d8a00443bd4bcbacc56e5e19b7294205cdc38f0
> Reviewed-on: https://webrtc-review.googlesource.com/61360
> Commit-Queue: Zhi Huang <zhihuang@webrtc.org>
> Reviewed-by: Steve Anton <steveanton@webrtc.org>
> Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#22613}

TBR=steveanton@webrtc.org,deadbeef@webrtc.org,zhihuang@webrtc.org

Change-Id: If245da9d1ce970ac8dab7f45015e9b268a5dbcbd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:8587
Reviewed-on: https://webrtc-review.googlesource.com/64860
Reviewed-by: Zhi Huang <zhihuang@webrtc.org>
Commit-Queue: Zhi Huang <zhihuang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22614}
diff --git a/pc/jseptransportcontroller.cc b/pc/jseptransportcontroller.cc
index 10725b5..5235791 100644
--- a/pc/jseptransportcontroller.cc
+++ b/pc/jseptransportcontroller.cc
@@ -457,13 +457,16 @@
     cricket::DtlsTransportInternal* rtp_dtls_transport,
     cricket::DtlsTransportInternal* rtcp_dtls_transport) {
   RTC_DCHECK(network_thread_->IsCurrent());
-
-  auto dtls_srtp_transport = rtc::MakeUnique<webrtc::DtlsSrtpTransport>(
-      rtcp_dtls_transport == nullptr);
+  bool rtcp_mux_enabled = rtcp_dtls_transport == nullptr;
+  auto srtp_transport =
+      rtc::MakeUnique<webrtc::SrtpTransport>(rtcp_mux_enabled);
   if (config_.enable_external_auth) {
-    dtls_srtp_transport->EnableExternalAuth();
+    srtp_transport->EnableExternalAuth();
   }
 
+  auto dtls_srtp_transport =
+      rtc::MakeUnique<webrtc::DtlsSrtpTransport>(std::move(srtp_transport));
+
   dtls_srtp_transport->SetDtlsTransports(rtp_dtls_transport,
                                          rtcp_dtls_transport);
   return dtls_srtp_transport;