Some cleanup in BaseChannel RTCP mux code.

webrtc/pc/rtcpmuxfilter.h

Index: webrtc/pc/rtcpmuxfilter.h
diff --git a/webrtc/pc/rtcpmuxfilter.h b/webrtc/pc/rtcpmuxfilter.h
index 94dc41d980e65d6a85dcda75b0682971e8837e80..91e790d684277406b57343996f2cbdce24e4f694 100644
--- a/webrtc/pc/rtcpmuxfilter.h
+++ b/webrtc/pc/rtcpmuxfilter.h
@@ -21,10 +21,20 @@ class RtcpMuxFilter {
  public:
   RtcpMuxFilter();
 
-  // Whether the filter is active, i.e. has RTCP mux been properly negotiated.
+  // Whether RTCP mux has been negotiated with a final answer (not provisional).
+  bool IsFullyActive() const;
+
+  // Whether RTCP mux has been negotiated with a provisional answer; this means
+  // a later answer could disable RTCP mux, and so the RTCP transport should
+  // not be disposed yet.
+  bool IsProvisionallyActive() const;
+
+  // Whether the filter is active, i.e. has RTCP mux been properly negotiated,
+  // either with a final or provisional answer.
   bool IsActive() const;
 
-  // Make the filter active, regardless of the current state.
+  // Make the filter active (fully, not provisionally) regardless of the
+  // current state. This should be used when an endpoint *requires* RTCP mux.
   void SetActive();
 
   // Specifies whether the offer indicates the use of RTCP mux.