android: add rollback RTCSdpType

BUG=webrtc:11796,webrtc:11970

Change-Id: I0047c7a050c344ef58735d9d0d6534b1ddf6c4d6
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/184263
Reviewed-by: Taylor <deadbeef@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/master@{#32243}

sdk/android/api/org/webrtc/SessionDescription.java

@@ -22,7 +22,8 @@ public class SessionDescription {
   public static enum Type {
     OFFER,
     PRANSWER,
-    ANSWER;
+    ANSWER,
+    ROLLBACK;
 
     public String canonicalForm() {
       return name().toLowerCase(Locale.US);

sdk/android/instrumentationtests/src/org/webrtc/PeerConnectionEndToEndTest.java

@@ -1488,6 +1488,38 @@ public void testRemoteStreamUpdatedWhenTracksAddedOrRemoved() throws Exception {
     factory.dispose();
   }
 
+  @Test
+  @SmallTest
+  public void testRollback() throws Exception {
+    PeerConnectionFactory factory = PeerConnectionFactory.builder().createPeerConnectionFactory();
+    PeerConnection.RTCConfiguration config = new PeerConnection.RTCConfiguration(Arrays.asList());
+    config.sdpSemantics = PeerConnection.SdpSemantics.UNIFIED_PLAN;
+
+    ObserverExpectations offeringExpectations = new ObserverExpectations("PCTest:offerer");
+    PeerConnection pc = factory.createPeerConnection(config, offeringExpectations);
+
+    SdpObserverLatch sdpLatch = new SdpObserverLatch();
+    pc.createOffer(sdpLatch, new MediaConstraints());
+    assertTrue(sdpLatch.await());
+    SessionDescription offer = sdpLatch.getSdp();
+
+    sdpLatch = new SdpObserverLatch();
+    offeringExpectations.expectSignalingChange(SignalingState.HAVE_LOCAL_OFFER);
+    pc.setLocalDescription(sdpLatch, offer);
+    assertTrue(sdpLatch.await());
+
+    SessionDescription rollback = new SessionDescription(SessionDescription.Type.ROLLBACK, "");
+    sdpLatch = new SdpObserverLatch();
+    offeringExpectations.expectSignalingChange(SignalingState.STABLE);
+    // TODO(bugs.webrtc.org/11970): determine if triggering ONN (twice even) is correct.
+    offeringExpectations.expectRenegotiationNeeded();
+    offeringExpectations.expectRenegotiationNeeded();
+    pc.setLocalDescription(sdpLatch, rollback);
+    assertTrue(sdpLatch.await());
+
+    assertTrue(offeringExpectations.waitForAllExpectationsToBeSatisfied(DEFAULT_TIMEOUT_SECONDS));
+  }
+
   private static void negotiate(PeerConnection offeringPC,
       ObserverExpectations offeringExpectations, PeerConnection answeringPC,
       ObserverExpectations answeringExpectations) {