Propogate network-worker thread split to api

BUG=webrtc:5645

Review-Url: https://codereview.webrtc.org/1968393002
Cr-Commit-Position: refs/heads/master@{#12767}
diff --git a/webrtc/api/peerconnectionfactory_unittest.cc b/webrtc/api/peerconnectionfactory_unittest.cc
index 963f1fe..de21e80 100644
--- a/webrtc/api/peerconnectionfactory_unittest.cc
+++ b/webrtc/api/peerconnectionfactory_unittest.cc
@@ -87,11 +87,9 @@
 #ifdef WEBRTC_ANDROID
     webrtc::InitializeAndroidObjects();
 #endif
-    factory_ = webrtc::CreatePeerConnectionFactory(rtc::Thread::Current(),
-                                                   rtc::Thread::Current(),
-                                                   NULL,
-                                                   NULL,
-                                                   NULL);
+    factory_ = webrtc::CreatePeerConnectionFactory(
+        rtc::Thread::Current(), rtc::Thread::Current(), rtc::Thread::Current(),
+        nullptr, nullptr, nullptr);
 
     ASSERT_TRUE(factory_.get() != NULL);
     port_allocator_.reset(