Add RSID-based demuxing to RtpDemuxer

webrtc/common_types.h

Index: webrtc/common_types.h
diff --git a/webrtc/common_types.h b/webrtc/common_types.h
index 424afd91397414a18c6f8d96e45da4d4a73f36db..76f2093bbbd267ea7eddb4f26bbe3fad15f2e719 100644
--- a/webrtc/common_types.h
+++ b/webrtc/common_types.h
@@ -707,6 +707,8 @@ class StreamId {
   // that can be encoded with one-byte header extensions.
   static constexpr size_t kMaxSize = 16;
 
+  static bool IsLegalName(const char* data, size_t size);

[danilchap, 2017/06/02 17:42:20]

until std::string_view is available, may be use rtc::ArrayView<const char>:
to stress data+size is one entity, not two independent.
bonus: std::string should be implicetly convertable to rtc::ArrayView<const
char>

May be do not use word 'Legal'
how about name 'IsValid'?

[eladalon, 2017/06/02 19:44:05]

1. About ArrayView - done.
2. About "valid" vs. "legal", I'm not sure. I was going to accept this
suggestion, but right before the search/replace, noticed that IsValidName() does
not occur anywhere in the codebase, but IsLegalName() does. In light of this,
wdyt?

[danilchap, 2017/06/07 13:45:41]

IsValidName doesn't occur, but IsValid occur way more often than IsLegal
(found only one class that use IsLegalName)

On the other side, it should be valid to put and use illegal name in this type.
i.e. IsLegalName probably better reflect what this function is checking.

+
   StreamId() { value_[0] = 0; }
   explicit StreamId(rtc::ArrayView<const char> value) {
     Set(value.data(), value.size());