Adding comments about threading around CreatePeerConnectionFactory.

webrtc/api/peerconnectionfactory.cc

 /*
  *  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 46 matching lines @@
   rtc::scoped_refptr<RefCountedDtlsIdentityStore> store_;
 };
 
 }  // anonymous namespace
 
 rtc::scoped_refptr<PeerConnectionFactoryInterface>
 CreatePeerConnectionFactory() {
   rtc::scoped_refptr<PeerConnectionFactory> pc_factory(
       new rtc::RefCountedObject<PeerConnectionFactory>());
 
-
-  // Call Initialize synchronously but make sure its executed on
-  // |signaling_thread|.
-  MethodCall0<PeerConnectionFactory, bool> call(
-      pc_factory.get(),
-      &PeerConnectionFactory::Initialize);
-  bool result =  call.Marshal(pc_factory->signaling_thread());
-
-  if (!result) {
-    return NULL;
+  RTC_CHECK(rtc::Thread::Current() == pc_factory->signaling_thread());
+  // The signaling thread is the current thread so we can
+  // safely call Initialize directly.
+  if (!pc_factory->Initialize()) {
+    return nullptr;
   }
   return PeerConnectionFactoryProxy::Create(pc_factory->signaling_thread(),
                                             pc_factory);
 }
 
 rtc::scoped_refptr<PeerConnectionFactoryInterface>
 CreatePeerConnectionFactory(
     rtc::Thread* worker_thread,
     rtc::Thread* signaling_thread,
     AudioDeviceModule* default_adm,
     cricket::WebRtcVideoEncoderFactory* encoder_factory,
     cricket::WebRtcVideoDecoderFactory* decoder_factory) {
   rtc::scoped_refptr<PeerConnectionFactory> pc_factory(
       new rtc::RefCountedObject<PeerConnectionFactory>(worker_thread,
                                                        signaling_thread,
                                                        default_adm,
                                                        encoder_factory,
                                                        decoder_factory));
 
   // Call Initialize synchronously but make sure its executed on
   // |signaling_thread|.
   MethodCall0<PeerConnectionFactory, bool> call(
       pc_factory.get(),
       &PeerConnectionFactory::Initialize);
   bool result =  call.Marshal(signaling_thread);
 
   if (!result) {
-    return NULL;
+    return nullptr;
   }
   return PeerConnectionFactoryProxy::Create(signaling_thread, pc_factory);
 }
 
 PeerConnectionFactory::PeerConnectionFactory()
     : owns_ptrs_(true),
       wraps_current_thread_(false),
       signaling_thread_(rtc::ThreadManager::Instance()->CurrentThread()),
       worker_thread_(new rtc::Thread) {
   if (!signaling_thread_) {
@@ skipping 241 matching lines @@
 }
 
 cricket::MediaEngineInterface* PeerConnectionFactory::CreateMediaEngine_w() {
   ASSERT(worker_thread_ == rtc::Thread::Current());
   return cricket::WebRtcMediaEngineFactory::Create(
       default_adm_.get(), video_encoder_factory_.get(),
       video_decoder_factory_.get());
 }
 
 }  // namespace webrtc