Refactor RtpSender and SSRCDatabase a bit.

webrtc/base/random.h

 /*
  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_BASE_RANDOM_H_
 #define WEBRTC_BASE_RANDOM_H_
 
 #include <limits>
 
 #include "webrtc/typedefs.h"
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/checks.h"
 
 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.
   // We need to limit the size to 32 bits to keep the output close to uniform.
   template <typename T>
   T Rand() {
     static_assert(std::numeric_limits<T>::is_integer &&
                       std::numeric_limits<T>::radix == 2 &&
                       std::numeric_limits<T>::digits <= 32,
                   "Rand is only supported for built-in integer types that are "
@@ skipping 39 matching lines @@
 template <>
 double Random::Rand<double>();
 
 // Return pseudo-random boolean value.
 template <>
 bool Random::Rand<bool>();
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_BASE_RANDOM_H_