Implement HTMLMediaElement::srcObject.

Source/core/html/HTMLMediaElement.h

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *
  * 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, this list of conditions and the following disclaimer in the
@@ skipping 41 matching lines @@
 #endif
 class AudioTrackList;
 class ContentType;
 class Event;
 class ExceptionState;
 class HTMLSourceElement;
 class HTMLTrackElement;
 class KURL;
 class MediaController;
 class MediaControls;
+class MediaProvider;
 class MediaError;
 class HTMLMediaSource;
 class TextTrackList;
 class TimeRanges;
 class URLRegistry;
 class VideoTrackList;
 
 typedef PODIntervalTree<double, TextTrackCue*> CueIntervalTree;
 typedef CueIntervalTree::IntervalType CueInterval;
 typedef Vector<CueInterval> CueList;
@@ skipping 32 matching lines @@
     };
     void scheduleDelayedAction(DelayedActionType);
 
     bool isActive() const { return m_active; }
 
     // error state
     PassRefPtrWillBeRawPtr<MediaError> error() const;
 
     // network state
     void setSrc(const AtomicString&);
+    MediaProvider* srcObject() const;
+    void setSrcObject(MediaProvider*);
     const KURL& currentSrc() const { return m_currentSrc; }
 
     enum NetworkState { NETWORK_EMPTY, NETWORK_IDLE, NETWORK_LOADING, NETWORK_NO_SOURCE };
     NetworkState networkState() const;
 
     String preload() const;
     void setPreload(const AtomicString&);
 
     PassRefPtrWillBeRawPtr<TimeRanges> buffered() const;
     void load();
@@ skipping 253 matching lines @@
     void checkIfSeekNeeded();
     void addPlayedRange(double start, double end);
 
     void scheduleTimeupdateEvent(bool periodicEvent);
     void scheduleEvent(const AtomicString& eventName); // FIXME: Rename to scheduleNamedEvent for clarity.
 
     // loading
     void prepareForLoad();
     void loadInternal();
     void selectMediaResource();
+    void loadResource(const KURL&);
     void loadResource(const KURL&, ContentType&, const String& keySystem);
     void startPlayerLoad();
     void setPlayerPreload();
     blink::WebMediaPlayer::LoadType loadType() const;
     void scheduleNextSourceChild();
+    void loadFromObject();
+    void loadFromAttribute();
     void loadNextSourceChild();
     void userCancelledLoad();
     void clearMediaPlayer(int flags);
     void clearMediaPlayerAndAudioSourceProviderClientWithoutLocking();
     bool havePotentialSourceChild();
     void noneSupported();
     void mediaEngineError(PassRefPtrWillBeRawPtr<MediaError>);
     void cancelPendingEventsAndCallbacks();
     void waitForSourceChange();
     void prepareToPlay();
@@ skipping 97 matching lines @@
     // Cached duration to suppress duplicate events if duration unchanged.
     double m_duration;
 
     // The last time a timeupdate event was sent (wall clock).
     double m_lastTimeUpdateEventWallTime;
 
     // The default playback start position.
     double m_defaultPlaybackStartPosition;
 
     // Loading state.
-    enum LoadState { WaitingForSource, LoadingFromSrcAttr, LoadingFromSourceElement };
+    enum LoadState { WaitingForSource, LoadingFromSrcObject, LoadingFromSrcAttr, LoadingFromSourceElement };
     LoadState m_loadState;
+    RawPtrWillBeMember<MediaProvider> m_srcObject;

[sof, 2014/09/19 06:26:23]

Could you explain what keeps m_srcObject alive&valid in a non-Oilpan setting? If
it is held onto by someone else & guaranteed to live beyond the media element,
then it would be preferable to make that clear in a comment.

[perkj_chrome, 2014/09/19 10:48:06]

oh, good catch. This is probably not correct 
Is there a generic solution or do I have to make the same solution used by
EventTarget.h ? That defines ref and deref and use
DEFINE_EVENT_TARGET_REFCOUNTING?
Can I disable OILPAN for MediaStreams and test? 

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...


I was trying to understand how/if this works without OILPAN today if
createObjectURL is used used to register a MediaStream and the last reference
from JS to the MediaStream is abandonded. It looks like the MediaStream object
itself would not survive? 

[sof, 2014/09/19 13:06:11]

Yes, exactly - ref-forwarding is how this is usually addressed. A better example
might be DOMSettableTokenList here, i.e., you add a ref+deref pure virtual pair
to MediaProvider

#if !ENABLE(OILPAN)
    virtual void ref() = 0;
    virtual void deref() = 0;
#endif

and then provide impls on the objects implementing MediaProvider -- i.e., on
MediaSource:

#if !ENABLE(OILPAN)
    virtual void ref() OVERRIDE {
RefCountedGarbageCollected<MediaStream>::ref(); }
    virtual void deref() OVERRIDE {
RefCountedGarbageCollected<MediaStream>::deref(); }
#endif

As Oilpan is disabled by default, you don't have to do anything to compile&test.
It didn't look as if it would survie. Unless there are cycles to be concerned
with between the MediaProvider implementations and HTMLMediaElement, the latter
should keep a ref ptr to its srcObject, non Oilpan. It's simpler and more
regular with Oilpan, and the handling here looks correct to me.

     RefPtrWillBeMember<HTMLSourceElement> m_currentSourceNode;
     RefPtrWillBeMember<Node> m_nextChildNodeToConsider;
 
     // "Deferred loading" state (for preload=none).
     enum DeferredLoadState {
         // The load is not deferred.
         NotDeferred,
         // The load is deferred, and waiting for the task to set the
         // delaying-the-load-event flag (to false).
         WaitingForStopDelayingLoadEventTask,
@@ skipping 107 matching lines @@
 inline bool isHTMLMediaElement(const HTMLElement& element)
 {
     return isHTMLAudioElement(element) || isHTMLVideoElement(element);
 }
 
 DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(HTMLMediaElement);
 
 } // namespace blink
 
 #endif // HTMLMediaElement_h