Provide a default async resolver factory if none injected to PeerConnection.

Bug: None
Change-Id: I448497ec5c6e3fe8d0c69f827fc256e6bd8a566d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/165001
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Qingsi Wang <qingsi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30151}

pc/jsep_transport_controller_unittest.cc

@@ -99,9 +99,9 @@ class JsepTransportControllerTest : public JsepTransportController::Observer,
                              int64_t packet_time_us) { RTC_NOTREACHED(); };
     config.ice_transport_factory = fake_ice_transport_factory_.get();
     config.dtls_transport_factory = fake_dtls_transport_factory_.get();
-    // TODO(zstein): Provide an AsyncResolverFactory once it is required.
     transport_controller_ = std::make_unique<JsepTransportController>(
-        signaling_thread, network_thread, port_allocator, nullptr, config);
+        signaling_thread, network_thread, port_allocator,
+        nullptr /* async_resolver_factory */, config);
     ConnectTransportControllerSignals();
   }
 

pc/peer_connection_factory.cc

@@ -28,6 +28,7 @@
 #include "api/video_track_source_proxy.h"
 #include "media/base/rtp_data_engine.h"
 #include "media/sctp/sctp_transport.h"
+#include "p2p/base/basic_async_resolver_factory.h"
 #include "p2p/base/basic_packet_socket_factory.h"
 #include "p2p/base/default_ice_transport_factory.h"
 #include "p2p/client/basic_port_allocator.h"
@@ -270,15 +271,16 @@ PeerConnectionFactory::CreatePeerConnection(
     });
   }
 
+  if (!dependencies.async_resolver_factory) {
+    dependencies.async_resolver_factory =
+        std::make_unique<webrtc::BasicAsyncResolverFactory>();
+  }
+
   if (!dependencies.ice_transport_factory) {
     dependencies.ice_transport_factory =
         std::make_unique<DefaultIceTransportFactory>();
   }
 
-  // TODO(zstein): Once chromium injects its own AsyncResolverFactory, set
-  // |dependencies.async_resolver_factory| to a new
-  // |rtc::BasicAsyncResolverFactory| if no factory is provided.
-
   network_thread_->Invoke<void>(
       RTC_FROM_HERE,
       rtc::Bind(&cricket::PortAllocator::SetNetworkIgnoreMask,