Add thread accessors to Call.

Classes associated with the Call instance, need access to these threads
and/or awareness, for checking for thread correctness.

Bug: webrtc:11993
Change-Id: I93bcee0657875f211be2ec959b96f818fa9fd8a0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/215584
Reviewed-by: Markus Handell <handellm@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33772}
diff --git a/pc/rtp_sender_receiver_unittest.cc b/pc/rtp_sender_receiver_unittest.cc
index b0df8fc..625f29b 100644
--- a/pc/rtp_sender_receiver_unittest.cc
+++ b/pc/rtp_sender_receiver_unittest.cc
@@ -107,7 +107,7 @@
         // Create fake media engine/etc. so we can create channels to use to
         // test RtpSenders/RtpReceivers.
         media_engine_(new cricket::FakeMediaEngine()),
-        fake_call_(),
+        fake_call_(worker_thread_, network_thread_),
         local_stream_(MediaStream::Create(kStreamId1)) {
     worker_thread_->Invoke<void>(RTC_FROM_HERE, [&]() {
       channel_manager_ = cricket::ChannelManager::Create(