Allows injection of network controller factory in test fixture.

Bug: webrtc:9155
Change-Id: I929c4cde66ad6743b4a8df2df3abfa7593992977
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/134645
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27843}

test/call_test.h

@@ -204,6 +204,8 @@ class CallTest : public ::testing::Test {
   std::unique_ptr<FecControllerFactoryInterface> fec_controller_factory_;
   std::unique_ptr<NetworkStatePredictorFactoryInterface>
       network_state_predictor_factory_;
+  std::unique_ptr<NetworkControllerFactoryInterface>
+      network_controller_factory_;
 
   test::FunctionVideoEncoderFactory fake_encoder_factory_;
   int fake_encoder_max_bitrate_ = -1;