Reland of Adding the ability to create an RtpSender without a track.

talk/app/webrtc/peerconnectioninterface_unittest.cc

 /*
  * libjingle
  * Copyright 2012 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 2019 matching lines @@
   pc_->AddStream(reference_collection_->at(0));
   EXPECT_TRUE(DoSetLocalDescription(desc_1.release()));
   auto senders = pc_->GetSenders();
   EXPECT_EQ(4u, senders.size());
   EXPECT_TRUE(ContainsSender(senders, kAudioTracks[0]));
   EXPECT_TRUE(ContainsSender(senders, kVideoTracks[0]));
   EXPECT_TRUE(ContainsSender(senders, kAudioTracks[1]));
   EXPECT_TRUE(ContainsSender(senders, kVideoTracks[1]));
 
   // Remove an audio and video track.
+  pc_->RemoveStream(reference_collection_->at(0));
   rtc::scoped_ptr<SessionDescriptionInterface> desc_2;
   CreateSessionDescriptionAndReference(1, 1, desc_2.accept());
+  pc_->AddStream(reference_collection_->at(0));
   EXPECT_TRUE(DoSetLocalDescription(desc_2.release()));
   senders = pc_->GetSenders();
   EXPECT_EQ(2u, senders.size());
   EXPECT_TRUE(ContainsSender(senders, kAudioTracks[0]));
   EXPECT_TRUE(ContainsSender(senders, kVideoTracks[0]));
   EXPECT_FALSE(ContainsSender(senders, kAudioTracks[1]));
   EXPECT_FALSE(ContainsSender(senders, kVideoTracks[1]));
 }
 
 // This tests that an RtpSender is created when the local description is set
@@ skipping 273 matching lines @@
   FakeConstraints updated_answer_c;
   answer_c.SetMandatoryReceiveAudio(false);
   answer_c.SetMandatoryReceiveVideo(false);
 
   cricket::MediaSessionOptions updated_answer_options;
   EXPECT_TRUE(
       ParseConstraintsForAnswer(&updated_answer_c, &updated_answer_options));
   EXPECT_TRUE(updated_answer_options.has_audio());
   EXPECT_TRUE(updated_answer_options.has_video());
 }