[Oilpan] Move MediaStream{Source|Component|Descriptor} to Oilpan heap

third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h

Index: third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h
diff --git a/third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h b/third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h
index a7ab84147b152911bbaa6a7bd8268373cde98a62..7dc87f85756e490b529cdc53bf80970ec488d466 100644
--- a/third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h
+++ b/third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h
@@ -44,9 +44,9 @@
 
 namespace blink {
 
-class PLATFORM_EXPORT MediaStreamSource final : public RefCounted<MediaStreamSource> {
+class PLATFORM_EXPORT MediaStreamSource final : public GarbageCollectedFinalized<MediaStreamSource> {
 public:
-    class PLATFORM_EXPORT Observer {
+    class PLATFORM_EXPORT Observer : public GarbageCollectedMixin {
     public:
         virtual ~Observer() { }
         virtual void sourceChangedState() = 0;
@@ -68,7 +68,7 @@ public:
         ReadyStateEnded = 2
     };
 
-    static PassRefPtr<MediaStreamSource> create(const String& id, Type, const String& name, bool remote, bool readonly, ReadyState = ReadyStateLive, bool requiresConsumer = false);
+    static MediaStreamSource* create(const String& id, Type, const String& name, bool remote, bool readonly, ReadyState = ReadyStateLive, bool requiresConsumer = false);
 
     const String& id() const { return m_id; }
     Type type() const { return m_type; }
@@ -96,6 +96,8 @@ public:
     bool removeAudioConsumer(AudioDestinationConsumer*);
     const HeapHashSet<Member<AudioDestinationConsumer>>& audioConsumers() { return m_audioConsumers; }
 
+    DECLARE_TRACE();

[sof, 2015/09/30 09:27:34]

Observers will take care of eagerly removing themselves when being swept out,
but what about m_audioConsumers members? Do we assume that the embedder will
call removeAudioConsumer() for all before this MediaStreamSource* is let go of.

i.e., have you considered how this (now heap) object behaves in the face of lazy
sweeping?

[peria, 2015/10/01 09:11:53]

Yes, we can assume removeAudioConsure() calls happens while MediaStreamSource
is alive.
removeAudioConsure() is called only in
WebMediaStreamSource::removeAudioConsumer(),
and the pointer |m_private| for MediaStreamSource is checked to be non-null.

[sof, 2015/10/01 18:54:05]

To verify, when chasing around abstractions I know little of.. :), I found:

- WebMediaStreamSource keeps a Persistent<MediaStreamSource>
- WebAudioCapturerSource keeps a WebMediaStreamSource.
- It calls removeAudioConsumer() on destruction/stopping.
- WebRtcLocalAudioTrack keeps a scoped_refptr<WebAudioCapturerSource>.
- PeerConnectionDependencyFactory::CreateLocalAudioTrack() creates a
WebRtcLocalAudioTrack.
- It assigns that track object as ExtraData to WebMediaStreamTrack (by way of
setExtraData())
- setExtraData() assigns MediaStreamComponent::m_extraData.

That latter MediaStreamComponent keeps the MediaStreamSource alive by way of all
of these abstractions (which bottom out in a Persistent<> ref.) Hence,
MediaStreamComponent will be finalized first and will have all its audio
consumers removed (and observers on next GC), hence no need for altering the
eagerness of its finalization.

So, assuming that this MediaStreamComponent isn't dually kept alive from the
Persistent<MediaStreamSource> reference, this is all fine.

+
 private:
     MediaStreamSource(const String& id, Type, const String& name, bool remote, bool readonly, ReadyState, bool requiresConsumer);
 
@@ -106,14 +108,14 @@ private:
     bool m_readonly;
     ReadyState m_readyState;
     bool m_requiresConsumer;
-    Vector<Observer*> m_observers;
+    HeapVector<Member<Observer>> m_observers;

[haraken, 2015/10/02 02:27:15]

Can we make this HeapHashSet<WeakMember<Observer>>? Then we don't need to
unregister the observers explicitly.

[peria, 2015/10/02 03:20:51]

Done.

     Mutex m_audioConsumersLock;
-    PersistentHeapHashSet<Member<AudioDestinationConsumer>> m_audioConsumers;
+    HeapHashSet<Member<AudioDestinationConsumer>> m_audioConsumers;
     OwnPtr<ExtraData> m_extraData;
     WebMediaConstraints m_constraints;
 };
 
-typedef Vector<RefPtr<MediaStreamSource>> MediaStreamSourceVector;
+typedef HeapVector<Member<MediaStreamSource>> MediaStreamSourceVector;
 
 } // namespace blink