message: Set nativeObserver to 0 to avoid double release.
  Cr-Commit-Position: refs/heads/master@{#34029}
diff: @@ -123,6 +123,7 @@ public class DataChannel {
  public void unregisterObserver() {
  checkDataChannelExists();
  nativeUnregisterObserver(nativeObserver);
  + nativeObserver = 0;
  }
  public String label() {
  