Refactor RtpSender and SSRCDatabase a bit.

webrtc/base/random.h

Index: webrtc/base/random.h
diff --git a/webrtc/base/random.h b/webrtc/base/random.h
index 647b84c9c947b8d11f711012c9deb5e09b151d3f..cb7b9ebe4a7d90778671ae6f2eda2b5ca32fd2cb 100644
--- a/webrtc/base/random.h
+++ b/webrtc/base/random.h
@@ -21,6 +21,17 @@ namespace webrtc {
 
 class Random {
  public:
+  // TODO(tommi): Change this so that the seed can be initialized internally,
+  // e.g. by offering two ways of constructing or offer a static method that
+  // returns a seed that's suitable for initialization.
+  // The problem now is that callers are calling clock_->TimeInMicroseconds()
+  // which calls TickTime::Now().Ticks(), which can return a very low value on
+  // Mac and can result in a seed of 0 after conversion to microseconds.
+  // Besides the quality of the random seed being poor, this also requires
+  // the client to take on extra dependencies to generate a seed.
+  // If we go for a static seed generator in Random, we can use something from
+  // webrtc/base and make sure that it works the same way across platforms.
+  // See also discussion here: https://codereview.webrtc.org/1623543002/
   explicit Random(uint64_t seed);
 
   // Return pseudo-random integer of the specified type.