Oilpan: Use weak processing to stop a closed RTCPeerConnection

Source/modules/mediastream/RTCPeerConnection.cpp

Index: Source/modules/mediastream/RTCPeerConnection.cpp
diff --git a/Source/modules/mediastream/RTCPeerConnection.cpp b/Source/modules/mediastream/RTCPeerConnection.cpp
index 9fa043f41ad084136ab707cbb02866952bb0f86f..eefcc587293f561d1a0b93f752355af056aa9b55 100644
--- a/Source/modules/mediastream/RTCPeerConnection.cpp
+++ b/Source/modules/mediastream/RTCPeerConnection.cpp
@@ -220,10 +220,9 @@ RTCPeerConnection::~RTCPeerConnection()
     // We are assuming that a wrapper is always created when RTCPeerConnection is created.
     ASSERT(m_closed || m_stopped);
 
-    // FIXME: Oilpan: We can't call stop here since it touches m_dataChannels.
-    // Another way to ensure that data channels are stopped at RTCPeerConnection
-    // destruction is needed.
+#if !ENABLE(OILPAN)
     stop();
+#endif
 }
 
 void RTCPeerConnection::createOffer(PassOwnPtr<RTCSessionDescriptionCallback> successCallback, PassOwnPtr<RTCErrorCallback> errorCallback, const Dictionary& mediaConstraints, ExceptionState& exceptionState)
@@ -742,12 +741,19 @@ void RTCPeerConnection::dispatchScheduledEvent()
     events.clear();
 }
 
+void RTCPeerConnection::clearWeakMembers(Visitor* visitor)
+{
+    if (!visitor->isAlive(this) && m_closed)

[Mads Ager (chromium), 2014/06/18 08:19:50]

This will not work because weak processing only happens when the trace method is
called. The trace method is only called when the object is alive and therefore
this condition will always be false because we will only get here when
visitor->isAlive(this).

When the RTCPeerConnection dies, what we need to make sure is that the
RTCDataChannels are stopped (that is the only thing that RTCPeerConnection::stop
does that matters when RTCPeerConnection is dead).

So, we should add a weak pointer from RTCDataChannel to RTCPeerConnection and
add custom weak processing for that one to make sure that we call stop on the
DataChannel when it outlives the PeerConnection.

[keishi, 2014/06/18 08:56:58]

Done.

+        stop();
+}
+
 void RTCPeerConnection::trace(Visitor* visitor)
 {
     visitor->trace(m_localStreams);
     visitor->trace(m_remoteStreams);
     visitor->trace(m_dataChannels);
     visitor->trace(m_scheduledEvents);
+    visitor->registerWeakMembers<RTCPeerConnection, &RTCPeerConnection::clearWeakMembers>(this);
     EventTargetWithInlineData::trace(visitor);
 }