Add virtual Initialize methods to PortAllocator and NetworkManager.

webrtc/p2p/base/portallocator.h

 /*
  *  Copyright 2004 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.
  */
 
@@ skipping 203 matching lines @@
   std::string content_name_;
   int component_;
   std::string ice_ufrag_;
   std::string ice_pwd_;
 
   // SetIceParameters is an implementation detail which only PortAllocator
   // should be able to call.
   friend class PortAllocator;
 };
 
-// Note that this class should only be used on one thread.
-// This includes calling the destructor.
+// This class can be constructed on any thread, but every other method
+// (including the destructor) should be called on a different thread.

[skvlad, 2016/06/23 22:15:55]

Do we have a way to verify that the "other thread" is always the same? like a
lazily initialized version of the ThreadChecker? 
It'd be good if we can enforce that requirement.

[Taylor Brandstetter, 2016/06/23 22:59:07]

Yeah, we can call "DetachFromThread" in the constructor so that it's attached
when the next method is called. This is the pattern Chrome uses. However...
Chrome currently still calls some methods from the wrong thread. I'll add the
thread checking once Chrome starts relying on Initialize, which will fix that.

+// This allows constructing a PortAllocator subclass on one thread and
+// passing it into an object that uses it on a different thread.
 class PortAllocator : public sigslot::has_slots<> {
  public:
   PortAllocator() :
       flags_(kDefaultPortAllocatorFlags),
       min_port_(0),
       max_port_(0),
       step_delay_(kDefaultStepDelay),
       allow_tcp_listen_(true),
       candidate_filter_(CF_ALL) {
-    // This will allow us to have old behavior on non webrtc clients.
   }
   virtual ~PortAllocator() {}
 
+  // This should be called on the PortAllocator's thread before the
+  // PortAllocator is used. Subclasses may override this if necessary.
+  virtual void Initialize() {}
+
   // Set STUN and TURN servers to be used in future sessions, and set
   // candidate pool size, as described in JSEP.
   //
   // If the servers are changing and the candidate pool size is nonzero,
   // existing pooled sessions will be destroyed and new ones created.
   //
   // If the servers are not changing but the candidate pool size is,
   // pooled sessions will be either created or destroyed as necessary.
   void SetConfiguration(const ServerAddresses& stun_servers,
                         const std::vector<RelayServerConfig>& turn_servers,
@@ skipping 99 matching lines @@
   int target_pooled_session_count_ = 0;
   // This variable represents the total number of pooled sessions
   // both owned by this class and taken by TakePooledSession.
   int allocated_pooled_session_count_ = 0;
   std::deque<std::unique_ptr<PortAllocatorSession>> pooled_sessions_;
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_PORTALLOCATOR_H_