Allow PeerConnection to be garbage collected after close().

LayoutTests/fast/mediastream/RTCPeerConnection-lifetime.html

Index: LayoutTests/fast/mediastream/RTCPeerConnection-lifetime.html
diff --git a/LayoutTests/fast/mediastream/RTCPeerConnection-lifetime.html b/LayoutTests/fast/mediastream/RTCPeerConnection-lifetime.html
index 076e0d3e553f4cacd149eb520ef97d93f59698a3..9e9ac3f37465ab69f8ecb7a963010268c07a8fea 100644
--- a/LayoutTests/fast/mediastream/RTCPeerConnection-lifetime.html
+++ b/LayoutTests/fast/mediastream/RTCPeerConnection-lifetime.html
@@ -24,7 +24,7 @@ function dataChannelOpen()
     shouldNotThrow("dc.send('xyzzy');");
 }
 
-function createPeerConnection()
+function createPeerConnectionAndDataChannel()
 {
     // The Peer Connection object is leaked
     var pc = new webkitRTCPeerConnection({iceServers:[]}, null);
@@ -32,7 +32,24 @@ function createPeerConnection()
     dc.onopen = dataChannelOpen;
 }
 
-createPeerConnection();
+// Test that the PeerConnection object is gc'd if close is called.
+var pcA = new webkitRTCPeerConnection(null, null);
+observationA = internals.observeGC(pcA);
+pcA.close();
+pcA = null;
+gc();
+shouldBeTrue('observationA.wasCollected');
+observationA = null;
+
+// Test that the PeerConnection object is not gc'd if close is not called.

[haraken, 2014/06/15 13:43:57]

I'm fine with this behavior, but I'm a bit concerned that this behavior will
produce a lot of memory leak in real worlds. If people forget to call close()
explicitly, the peer connection starts leaking. (I understand this is a separate
discussion from this CL though.)

[Henrik Grunell, 2014/06/16 07:48:59]

Agree. The proposed spec change only says that it can be garbage collected if in
closed state. However, I have brought this up in a mail thread since it makes
sense if one does (as a trivial example)

var pc = new ...;
pc = null;

that it should be gc'd. I see that a follow-up if that should be done. This CL
does improve the current state where when we never allow gc at all (unless stop
is called).

+var pcB = new webkitRTCPeerConnection(null, null);
+observationB = internals.observeGC(pcB);
+pcB = null;
+gc();
+shouldBeFalse('observationB.wasCollected');
+observationB = null;
+
+createPeerConnectionAndDataChannel();
 gc();
 
 window.jsTestIsAsync = true;