Stop using DEPRECATED_SingleThreadedTaskQueueForTesting in call tests

This is practiaclly a reland of the
https://webrtc-review.googlesource.com/c/src/+/157896
except that video multi stream tests are still using the deprecated TaskQueue
(see https://webrtc-review.googlesource.com/c/src/+/159280)

Bug: webrtc:10933
Change-Id: Ie715345924f9dd2d7dd52c99de3ea595b6fad5ae
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/159699
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29794}
diff --git a/test/call_test.h b/test/call_test.h
index 6224a6e..ba9740d 100644
--- a/test/call_test.h
+++ b/test/call_test.h
@@ -30,7 +30,6 @@
 #include "test/fake_vp8_encoder.h"
 #include "test/frame_generator_capturer.h"
 #include "test/rtp_rtcp_observer.h"
-#include "test/single_threaded_task_queue.h"
 
 namespace webrtc {
 namespace test {
@@ -174,7 +173,7 @@
   void SetVideoEncoderConfig(const VideoEncoderConfig& config);
   VideoSendStream* GetVideoSendStream();
   FlexfecReceiveStream::Config* GetFlexFecConfig();
-  TaskQueueBase* task_queue() { return &task_queue_; }
+  TaskQueueBase* task_queue() { return task_queue_.get(); }
 
   Clock* const clock_;
 
@@ -230,7 +229,7 @@
   void AddRtpExtensionByUri(const std::string& uri,
                             std::vector<RtpExtension>* extensions) const;
 
-  DEPRECATED_SingleThreadedTaskQueueForTesting task_queue_;
+  std::unique_ptr<TaskQueueBase, TaskQueueDeleter> task_queue_;
   std::vector<RtpExtension> rtp_extensions_;
   rtc::scoped_refptr<AudioProcessing> apm_send_;
   rtc::scoped_refptr<AudioProcessing> apm_recv_;