DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Implementation

Mercurial (bffa34334d58)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef NSDOMMEDIASTREAM_H_
#define NSDOMMEDIASTREAM_H_

#include "ImageContainer.h"

#include "nsAutoPtr.h"
#include "nsCycleCollectionParticipant.h"
#include "nsWrapperCache.h"
#include "StreamTracks.h"
#include "nsIDOMWindow.h"
#include "nsIPrincipal.h"
#include "MediaTrackConstraints.h"
#include "mozilla/DOMEventTargetHelper.h"
#include "mozilla/RelativeTimeline.h"
#include "PrincipalChangeObserver.h"

namespace mozilla {

class AbstractThread;
class DOMMediaStream;
class MediaStream;
class MediaInputPort;
class MediaStreamGraph;
class ProcessedMediaStream;

enum class BlockingMode;

namespace dom {
class AudioNode;
class HTMLCanvasElement;
class MediaStreamTrack;
class MediaStreamTrackSource;
class AudioStreamTrack;
class VideoStreamTrack;
class AudioTrack;
class VideoTrack;
class AudioTrackList;
class VideoTrackList;
class MediaTrackListListener;
}  // namespace dom

namespace layers {
class ImageContainer;
class OverlayImage;
}  // namespace layers

#define NS_DOMMEDIASTREAM_IID                        \
  {                                                  \
    0x8cb65468, 0x66c0, 0x444e, {                    \
      0x89, 0x9f, 0x89, 0x1d, 0x9e, 0xd2, 0xbe, 0x7c \
    }                                                \
  }

/**

// clang-format off
 * DOM wrapper for MediaStreams.
 *
 * To account for track operations such as clone(), addTrack() and
 * removeTrack(), a DOMMediaStream wraps three internal (and chained)
 * MediaStreams:
 *   1. mInputStream
 *      - Controlled by the owner/source of the DOMMediaStream.
 *        It's a stream of the type indicated by
 *      - DOMMediaStream::CreateSourceStream/CreateTrackUnionStream. A source
 *        typically creates its DOMMediaStream, creates the MediaStreamTracks
 *        owned by said stream, then gets the internal input stream to which it
 *        feeds data for the previously created tracks.
 *      - When necessary it can create tracks on the internal stream only and
 *        their corresponding MediaStreamTracks will be asynchronously created.
 *   2. mOwnedStream
 *      - A TrackUnionStream containing tracks owned by this stream.
 *      - The internal model of a MediaStreamTrack consists of its owning
 *        DOMMediaStream and the TrackID of the corresponding internal track in
 *        the owning DOMMediaStream's mOwnedStream.
 *      - The owned stream is different from the input stream since a cloned
 *        DOMMediaStream is also the owner of its (cloned) MediaStreamTracks.
 *      - Stopping an original track shall not stop its clone. This is
 *        solved by stopping it at the owned stream, while the clone's owned
 *        stream gets data directly from the original input stream.
 *      - A DOMMediaStream (original or clone) gets all tracks dynamically
 *        added by the source automatically forwarded by having a TRACK_ANY
 *        MediaInputPort set up from the owning DOMMediaStream's input stream
 *        to this DOMMediaStream's owned stream.
 *   3. mPlaybackStream
 *      - A TrackUnionStream containing the tracks corresponding to the
 *        MediaStreamTracks currently in this DOMMediaStream (per getTracks()).
 *      - Similarly as for mOwnedStream, there's a TRACK_ANY MediaInputPort set
 *        up from the owned stream to the playback stream to allow tracks
 *        dynamically added by the source to be automatically forwarded to any
 *        audio or video sinks.
 *      - MediaStreamTracks added by addTrack() are set up with a MediaInputPort
 *        locked to their internal TrackID, from their owning DOMMediaStream's
 *        owned stream to this playback stream.
 *
 *
 * A graphical representation of how tracks are connected in various cases as
 * follows:
 *
 *                     addTrack()ed case:
 * DOMStream A
 *           Input        Owned          Playback
 *            t1 ---------> t1 ------------> t1     <- MediaStreamTrack X
 *                                                     (pointing to t1 in A)
 *                                 --------> t2     <- MediaStreamTrack Y
 *                                /                    (pointing to t1 in B)
 * DOMStream B                   /
 *           Input        Owned /        Playback
 *            t1 ---------> t1 ------------> t1     <- MediaStreamTrack Y
 *                                                     (pointing to t1 in B)
 *
 *                     removeTrack()ed case:
 * DOMStream A
 *           Input        Owned          Playback
 *            t1 ---------> t1                      <- No tracks
 *
 *
 *                     clone()d case:
 * DOMStream A
 *           Input        Owned          Playback
 *            t1 ---------> t1 ------------> t1     <- MediaStreamTrack X
 *               \                                     (pointing to t1 in A)
 *                -----
 * DOMStream B         \
 *           Input      \ Owned          Playback
 *                       -> t1 ------------> t1     <- MediaStreamTrack Y
 *                                                     (pointing to t1 in B)
 *
 *
 *            addTrack()ed, removeTrack()ed and clone()d case:
 *
 *  Here we have done the following:
 *    var A = someStreamWithTwoTracks;
 *    var B = someStreamWithOneTrack;
 *    var X = A.getTracks()[0];
 *    var Y = A.getTracks()[1];
 *    var Z = B.getTracks()[0];
 *    A.addTrack(Z);
 *    A.removeTrack(X);
 *    B.removeTrack(Z);
 *    var A' = A.clone();
 *
 * DOMStream A
 *           Input        Owned          Playback
 *            t1 ---------> t1                      <- MediaStreamTrack X
 *                                                     (removed)
 *                                                     (pointing to t1 in A)
 *            t2 ---------> t2 ------------> t2     <- MediaStreamTrack Y
 *             \                                       (pointing to t2 in A)
 *              \                    ------> t3     <- MediaStreamTrack Z
 *               \                  /                  (pointing to t1 in B)
 * DOMStream B    \                /
 *           Input \      Owned   /      Playback
 *            t1 ---^-----> t1 ---                  <- MediaStreamTrack Z
 *                                                     (removed)
 *              \    \                                 (pointing to t1 in B)
 *               \    \
 * DOMStream A'   \    \
 *           Input \    \ Owned          Playback
 *                  \    -> t1 ------------> t1     <- MediaStreamTrack Y'
 *                   \                                 (pointing to t1 in A')
 *                    ----> t2 ------------> t2     <- MediaStreamTrack Z'
 *                                                     (pointing to t2 in A')
 */
// clang-format on
class DOMMediaStream
    : public DOMEventTargetHelper,
      public dom::PrincipalChangeObserver<dom::MediaStreamTrack>,
      public RelativeTimeline,
      public SupportsWeakPtr<DOMMediaStream> {
  friend class dom::MediaStreamTrack;
  typedef dom::MediaStreamTrack MediaStreamTrack;
  typedef dom::AudioStreamTrack AudioStreamTrack;
  typedef dom::VideoStreamTrack VideoStreamTrack;
  typedef dom::MediaStreamTrackSource MediaStreamTrackSource;
  typedef dom::AudioTrack AudioTrack;
  typedef dom::VideoTrack VideoTrack;
  typedef dom::AudioTrackList AudioTrackList;
  typedef dom::VideoTrackList VideoTrackList;

 public:
  typedef dom::MediaTrackConstraints MediaTrackConstraints;

  MOZ_DECLARE_WEAKREFERENCE_TYPENAME(DOMMediaStream)

  class TrackListener {
   public:
    virtual ~TrackListener() {}

    /**
     * Called when the DOMMediaStream has a live track added, either by
     * script (addTrack()) or the source creating one.
     */
    virtual void NotifyTrackAdded(const RefPtr<MediaStreamTrack>& aTrack){};

    /**
     * Called when the DOMMediaStream removes a live track from playback, either
     * by script (removeTrack(), track.stop()) or the source ending it.
     */
    virtual void NotifyTrackRemoved(const RefPtr<MediaStreamTrack>& aTrack){};

    /**
     * Called when the DOMMediaStream has become active.
     */
    virtual void NotifyActive(){};

    /**
     * Called when the DOMMediaStream has become inactive.
     */
    virtual void NotifyInactive(){};
  };

  /**
   * TrackPort is a representation of a MediaStreamTrack-MediaInputPort pair
   * that make up a link between the Owned stream and the Playback stream.
   *
   * Semantically, the track is the identifier/key and the port the value of
   * this connection.
   *
   * The input port can be shared between several TrackPorts. This is the case
   * for DOMMediaStream's mPlaybackPort which forwards all tracks in its
   * mOwnedStream automatically.
   *
   * If the MediaStreamTrack is owned by another DOMMediaStream (called A) than
   * the one owning the TrackPort (called B), the input port (locked to the
   * MediaStreamTrack's TrackID) connects A's mOwnedStream to B's
   * mPlaybackStream.
   *
   * A TrackPort may never leave the DOMMediaStream it was created in. Internal
   * use only.
   */
  class TrackPort {
   public:
    NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(TrackPort)
    NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS(TrackPort)

    /**
     * Indicates MediaInputPort ownership to the TrackPort.
     *
     * OWNED    - Owned by the TrackPort itself. TrackPort must destroy the
     *            input port when it's destructed.
     * EXTERNAL - Owned by another entity. It's the caller's responsibility to
     *            ensure the the MediaInputPort outlives the TrackPort.
     */
    enum class InputPortOwnership { OWNED = 1, EXTERNAL };

    TrackPort(MediaInputPort* aInputPort, MediaStreamTrack* aTrack,
              const InputPortOwnership aOwnership);

   protected:
    virtual ~TrackPort();

   public:
    void DestroyInputPort();

    /**
     * Returns the source stream of the input port.
     */
    MediaStream* GetSource() const;

    /**
     * Returns the track ID this track is locked to in the source stream of the
     * input port.
     */
    TrackID GetSourceTrackId() const;

    MediaInputPort* GetInputPort() const { return mInputPort; }
    MediaStreamTrack* GetTrack() const { return mTrack; }

    /**
     * Blocks aTrackId from going into mInputPort unless the port has been
     * destroyed. Returns a promise that gets resolved when the MediaStreamGraph
     * has applied the block in the playback stream.
     */
    RefPtr<GenericPromise> BlockSourceTrackId(TrackID aTrackId,
                                              BlockingMode aBlockingMode);

   private:
    RefPtr<MediaInputPort> mInputPort;
    RefPtr<MediaStreamTrack> mTrack;

    // Defines if we've been given ownership of the input port or if it's owned
    // externally. The owner is responsible for destroying the port.
    const InputPortOwnership mOwnership;
  };

  explicit DOMMediaStream(nsPIDOMWindowInner* aWindow);

  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(DOMMediaStream, DOMEventTargetHelper)
  NS_DECLARE_STATIC_IID_ACCESSOR(NS_DOMMEDIASTREAM_IID)

  nsPIDOMWindowInner* GetParentObject() const { return mWindow; }
  virtual JSObject* WrapObject(JSContext* aCx,
                               JS::Handle<JSObject*> aGivenProto) override;

  // WebIDL

  static already_AddRefed<DOMMediaStream> Constructor(
      const dom::GlobalObject& aGlobal, ErrorResult& aRv);

  static already_AddRefed<DOMMediaStream> Constructor(
      const dom::GlobalObject& aGlobal, const DOMMediaStream& aStream,
      ErrorResult& aRv);

  static already_AddRefed<DOMMediaStream> Constructor(
      const dom::GlobalObject& aGlobal,
      const dom::Sequence<OwningNonNull<MediaStreamTrack>>& aTracks,
      ErrorResult& aRv);

  static already_AddRefed<dom::Promise> CountUnderlyingStreams(
      const dom::GlobalObject& aGlobal, ErrorResult& aRv);

  void GetId(nsAString& aID) const;

  void GetAudioTracks(nsTArray<RefPtr<AudioStreamTrack>>& aTracks) const;
  void GetAudioTracks(nsTArray<RefPtr<MediaStreamTrack>>& aTracks) const;
  void GetVideoTracks(nsTArray<RefPtr<VideoStreamTrack>>& aTracks) const;
  void GetVideoTracks(nsTArray<RefPtr<MediaStreamTrack>>& aTracks) const;
  void GetTracks(nsTArray<RefPtr<MediaStreamTrack>>& aTracks) const;
  MediaStreamTrack* GetTrackById(const nsAString& aId) const;
  void AddTrack(MediaStreamTrack& aTrack);
  void RemoveTrack(MediaStreamTrack& aTrack);
  already_AddRefed<DOMMediaStream> Clone();

  bool Active() const;

  IMPL_EVENT_HANDLER(addtrack)
  IMPL_EVENT_HANDLER(removetrack)

  // NON-WebIDL

  MediaStreamTrack* GetOwnedTrackById(const nsAString& aId);

  /**
   * Returns true if this DOMMediaStream has aTrack in its mPlaybackStream.
   */
  bool HasTrack(const MediaStreamTrack& aTrack) const;

  /**
   * Returns true if this DOMMediaStream owns aTrack.
   */
  bool OwnsTrack(const MediaStreamTrack& aTrack) const;

  /**
   * Returns the corresponding MediaStreamTrack if it's in our mOwnedStream.
   * aInputTrackID should match the track's TrackID in its input stream,
   * and aTrackID the TrackID in mOwnedStream.
   *
   * When aTrackID is not supplied or set to TRACK_ANY, we return the first
   * MediaStreamTrack that matches the given input track. Note that there may
   * be multiple MediaStreamTracks matching the same input track, but that they
   * in that case all share the same MediaStreamTrackSource.
   */
  MediaStreamTrack* FindOwnedDOMTrack(MediaStream* aInputStream,
                                      TrackID aInputTrackID,
                                      TrackID aTrackID = TRACK_ANY) const;

  /**
   * Returns the TrackPort connecting aTrack's input stream to mOwnedStream,
   * or nullptr if aTrack is not owned by this DOMMediaStream.
   */
  TrackPort* FindOwnedTrackPort(const MediaStreamTrack& aTrack) const;

  /**
   * Returns the corresponding MediaStreamTrack if it's in our mPlaybackStream.
   * aInputTrackID should match the track's TrackID in its owned stream.
   */
  MediaStreamTrack* FindPlaybackDOMTrack(MediaStream* aInputStream,
                                         TrackID aInputTrackID) const;

  /**
   * Returns the TrackPort connecting mOwnedStream to mPlaybackStream for
   * aTrack.
   */
  TrackPort* FindPlaybackTrackPort(const MediaStreamTrack& aTrack) const;

  MediaStream* GetInputStream() const { return mInputStream; }
  ProcessedMediaStream* GetOwnedStream() const { return mOwnedStream; }
  ProcessedMediaStream* GetPlaybackStream() const { return mPlaybackStream; }

  /**
   * Allows a video element to identify this stream as a camera stream, which
   * needs special treatment.
   */
  virtual MediaStream* GetCameraStream() const { return nullptr; }

  /**
   * Legacy method that returns true when the playback stream has finished.
   */
  bool IsFinished() const;

  TrackRate GraphRate();

  /**
   * Returns a principal indicating who may access this stream. The stream
   * contents can only be accessed by principals subsuming this principal.
   */
  nsIPrincipal* GetPrincipal() { return mPrincipal; }

  /**
   * Returns a principal indicating who may access video data of this stream.
   * The video principal will be a combination of all live video tracks.
   */
  nsIPrincipal* GetVideoPrincipal() { return mVideoPrincipal; }

  // From PrincipalChangeObserver<MediaStreamTrack>.
  void PrincipalChanged(MediaStreamTrack* aTrack) override;

  /**
   * Add a PrincipalChangeObserver to this stream.
   *
   * Returns true if it was successfully added.
   *
   * Ownership of the PrincipalChangeObserver remains with the caller, and it's
   * the caller's responsibility to remove the observer before it dies.
   */
  bool AddPrincipalChangeObserver(
      dom::PrincipalChangeObserver<DOMMediaStream>* aObserver);

  /**
   * Remove an added PrincipalChangeObserver from this stream.
   *
   * Returns true if it was successfully removed.
   */
  bool RemovePrincipalChangeObserver(
      dom::PrincipalChangeObserver<DOMMediaStream>* aObserver);

  // Webrtc allows the remote side to name a stream whatever it wants, and we
  // need to surface this to content.
  void AssignId(const nsAString& aID) { mID = aID; }

  /**
   * Create a DOMMediaStream whose underlying input stream is a
   * SourceMediaStream.
   */
  static already_AddRefed<DOMMediaStream> CreateSourceStreamAsInput(
      nsPIDOMWindowInner* aWindow, MediaStreamGraph* aGraph);

  /**
   * Create a DOMMediaStream whose underlying input stream is a
   * TrackUnionStream.
   */
  static already_AddRefed<DOMMediaStream> CreateTrackUnionStreamAsInput(
      nsPIDOMWindowInner* aWindow, MediaStreamGraph* aGraph);

  /**
   * Create an DOMMediaStream whose underlying input stream is an
   * AudioCaptureStream.
   */
  static already_AddRefed<DOMMediaStream> CreateAudioCaptureStreamAsInput(
      nsPIDOMWindowInner* aWindow, nsIPrincipal* aPrincipal,
      MediaStreamGraph* aGraph);

  /**
   * Adds a MediaStreamTrack to mTracks and raises "addtrack".
   *
   * Note that "addtrack" is raised synchronously and only has an effect if
   * this MediaStream is already exposed to script. For spec compliance this is
   * to be called from an async task.
   */
  void AddTrackInternal(MediaStreamTrack* aTrack);

  /**
   * Called for each track in our owned stream to indicate to JS that we
   * are carrying that track.
   *
   * Pre-creates a MediaStreamTrack and returns it.
   * It is up to the caller to make sure it is added through AddTrackInternal.
   */
  already_AddRefed<MediaStreamTrack> CreateDOMTrack(
      TrackID aTrackID, MediaSegment::Type aType,
      MediaStreamTrackSource* aSource,
      const MediaTrackConstraints& aConstraints = MediaTrackConstraints());

  /**
   * Creates a MediaStreamTrack cloned from aTrack, adds it to mTracks and
   * returns it.
   * aCloneTrackID is the TrackID the new track will get in mOwnedStream.
   */
  already_AddRefed<MediaStreamTrack> CloneDOMTrack(MediaStreamTrack& aTrack,
                                                   TrackID aCloneTrackID);

  /**
   * Add an nsISupports object that this stream will keep alive as long as
   * the stream itself is alive.
   */
  void AddConsumerToKeepAlive(nsISupports* aConsumer) {
    mConsumersToKeepAlive.AppendElement(aConsumer);
  }

  // Registers a track listener to this MediaStream, for listening to changes
  // to our track set. The caller must call UnregisterTrackListener before
  // being destroyed, so we don't hold on to a dead pointer. Main thread only.
  void RegisterTrackListener(TrackListener* aListener);

  // Unregisters a track listener from this MediaStream. The caller must call
  // UnregisterTrackListener before being destroyed, so we don't hold on to
  // a dead pointer. Main thread only.
  void UnregisterTrackListener(TrackListener* aListener);

  // Tells this MediaStream whether it can go inactive as soon as no tracks
  // are live anymore.
  void SetFinishedOnInactive(bool aFinishedOnInactive);

 protected:
  virtual ~DOMMediaStream();

  void Destroy();
  void InitSourceStream(MediaStreamGraph* aGraph);
  void InitTrackUnionStream(MediaStreamGraph* aGraph);
  void InitAudioCaptureStream(nsIPrincipal* aPrincipal,
                              MediaStreamGraph* aGraph);

  // Sets up aStream as mInputStream. A producer may append data to a
  // SourceMediaStream input stream, or connect another stream to a
  // TrackUnionStream input stream.
  void InitInputStreamCommon(MediaStream* aStream, MediaStreamGraph* aGraph);

  // Sets up a new TrackUnionStream as mOwnedStream and connects it to
  // mInputStream with a TRACK_ANY MediaInputPort if available.
  // If this DOMMediaStream should have an input stream (producing data),
  // it has to be initiated before the owned stream.
  void InitOwnedStreamCommon(MediaStreamGraph* aGraph);

  // Sets up a new TrackUnionStream as mPlaybackStream and connects it to
  // mOwnedStream with a TRACK_ANY MediaInputPort if available.
  // If this DOMMediaStream should have an owned stream (producer or clone),
  // it has to be initiated before the playback stream.
  void InitPlaybackStreamCommon(MediaStreamGraph* aGraph);

  // Dispatches NotifyActive() to all registered track listeners.
  void NotifyActive();

  // Dispatches NotifyInactive() to all registered track listeners.
  void NotifyInactive();

  // Dispatches NotifyTrackAdded() to all registered track listeners.
  void NotifyTrackAdded(const RefPtr<MediaStreamTrack>& aTrack);

  // Dispatches NotifyTrackRemoved() to all registered track listeners.
  void NotifyTrackRemoved(const RefPtr<MediaStreamTrack>& aTrack);

  // Dispatches "addtrack" or "removetrack".
  nsresult DispatchTrackEvent(const nsAString& aName,
                              const RefPtr<MediaStreamTrack>& aTrack);

  class PlaybackTrackListener;
  friend class PlaybackTrackListener;

  /**
   * Block a track in our playback stream. Calls NotifyPlaybackTrackBlocked()
   * after the MediaStreamGraph has applied the block and the track is no longer
   * live.
   */
  void BlockPlaybackTrack(TrackPort* aTrack);

  /**
   * Called on main thread after MediaStreamGraph has applied a track block in
   * our playback stream.
   */
  void NotifyPlaybackTrackBlocked();

  // Recomputes the current principal of this stream based on the set of tracks
  // it currently contains. PrincipalChangeObservers will be notified only if
  // the principal changes.
  void RecomputePrincipal();

  // We need this to track our parent object.
  nsCOMPtr<nsPIDOMWindowInner> mWindow;

  // MediaStreams are owned by the graph, but we tell them when to die,
  // and they won't die until we let them.

  // This stream contains tracks used as input by us. Cloning happens from this
  // stream. Tracks may exist in these stream but not in |mOwnedStream| if they
  // have been stopped.
  MediaStream* mInputStream;

  // This stream contains tracks owned by us (if we were created directly from
  // source, or cloned from some other stream). Tracks map to |mOwnedTracks|.
  ProcessedMediaStream* mOwnedStream;

  // This stream contains tracks currently played by us, despite of owner.
  // Tracks map to |mTracks|.
  ProcessedMediaStream* mPlaybackStream;

  // This port connects mInputStream to mOwnedStream. All tracks forwarded.
  RefPtr<MediaInputPort> mOwnedPort;

  // This port connects mOwnedStream to mPlaybackStream. All tracks not
  // explicitly blocked due to removal are forwarded.
  RefPtr<MediaInputPort> mPlaybackPort;

  // MediaStreamTracks corresponding to tracks in our mOwnedStream.
  AutoTArray<RefPtr<TrackPort>, 2> mOwnedTracks;

  // MediaStreamTracks corresponding to tracks in our mPlaybackStream.
  AutoTArray<RefPtr<TrackPort>, 2> mTracks;

  // Number of MediaStreamTracks that have been removed on main thread but are
  // waiting to be removed on MediaStreamGraph thread.
  size_t mTracksPendingRemoval;

  // Listener tracking when live MediaStreamTracks in mTracks end.
  RefPtr<PlaybackTrackListener> mPlaybackTrackListener;

  // Set to true after MediaStreamGraph has created tracks for mPlaybackStream.
  bool mTracksCreated;

  nsString mID;

  // Keep these alive while the stream is alive.
  nsTArray<nsCOMPtr<nsISupports>> mConsumersToKeepAlive;

  bool mNotifiedOfMediaStreamGraphShutdown;

  // The track listeners subscribe to changes in this stream's track set.
  nsTArray<TrackListener*> mTrackListeners;

  // True if this stream has live tracks.
  bool mActive;

  // For compatibility with mozCaptureStream, we in some cases do not go
  // inactive until the MediaDecoder lets us. (Remove this in Bug 1302379)
  bool mFinishedOnInactive;

 private:
  void NotifyPrincipalChanged();
  // Principal identifying who may access the collected contents of this stream.
  // If null, this stream can be used by anyone because it has no content yet.
  nsCOMPtr<nsIPrincipal> mPrincipal;
  // Video principal is used by video element as access is requested to its
  // image data.
  nsCOMPtr<nsIPrincipal> mVideoPrincipal;
  nsTArray<dom::PrincipalChangeObserver<DOMMediaStream>*>
      mPrincipalChangeObservers;
  CORSMode mCORSMode;
};

NS_DEFINE_STATIC_IID_ACCESSOR(DOMMediaStream, NS_DOMMEDIASTREAM_IID)

class DOMAudioNodeMediaStream : public DOMMediaStream {
  typedef dom::AudioNode AudioNode;

 public:
  DOMAudioNodeMediaStream(nsPIDOMWindowInner* aWindow, AudioNode* aNode);

  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(DOMAudioNodeMediaStream,
                                           DOMMediaStream)

  /**
   * Create a DOMAudioNodeMediaStream whose underlying stream is a
   * TrackUnionStream.
   */
  static already_AddRefed<DOMAudioNodeMediaStream>
  CreateTrackUnionStreamAsInput(nsPIDOMWindowInner* aWindow, AudioNode* aNode,
                                MediaStreamGraph* aGraph);

 protected:
  ~DOMAudioNodeMediaStream();

 private:
  // If this object wraps a stream owned by an AudioNode, we need to ensure that
  // the node isn't cycle-collected too early.
  RefPtr<AudioNode> mStreamNode;
};

}  // namespace mozilla

#endif /* NSDOMMEDIASTREAM_H_ */