message: Delete forward declarations from peer_connection_interface.h
  Cr-Commit-Position: refs/heads/master@{#29191}
diff: #include "api/call/call_factory_interface.h"
  #include "api/crypto/crypto_options.h"
  #include "api/data_channel_interface.h"
  +#include "api/dtls_transport_interface.h"
  #include "api/fec_controller.h"
  #include "api/jsep.h"
  #include "api/media_stream_interface.h"
  #include "api/rtp_receiver_interface.h"
  #include "api/rtp_sender_interface.h"
  #include "api/rtp_transceiver_interface.h"
  +#include "api/sctp_transport_interface.h"
  #include "api/set_remote_description_observer_interface.h"
  #include "api/stats/rtc_stats_collector_callback.h"
  #include "api/stats_types.h"
  #include "rtc_base/system/rtc_export.h"
  namespace rtc {
  -class SSLIdentity;
  class Thread;
  } // namespace rtc
  namespace webrtc {
  -class AudioDeviceModule;
  -class AudioMixer;
  -class AudioProcessing;
  -class DtlsTransportInterface;
  -class SctpTransportInterface;
  -class VideoDecoderFactory;
  -class VideoEncoderFactory;
  // MediaStream container interface.
  class StreamCollectionInterface : public rtc::RefCountInterface {
  