Fix issue of localDescription and remoteDescription getter.

Source/modules/mediastream/RTCPeerConnection.cpp

 /*
  * Copyright (C) 2012 Google 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
@@ skipping 257 matching lines @@
     }
 
     document->frame()->loader().client()->dispatchWillStartUsingPeerConnectionHandler(m_peerHandler.get());
 
     if (!m_peerHandler->initialize(configuration, constraints)) {
         m_closed = true;
         m_stopped = true;
         exceptionState.throwDOMException(NotSupportedError, "Failed to initialize native PeerConnection.");
         return;
     }
+    m_localDescription = RTCSessionDescription::create(context, m_peerHandler->localDescription());
+    m_remoteDescription = RTCSessionDescription::create(context, m_peerHandler->remoteDescription());
 }
 
 RTCPeerConnection::~RTCPeerConnection()
 {
     // This checks that close() or stop() is called before the destructor.
     // We are assuming that a wrapper is always created when RTCPeerConnection is created.
     ASSERT(m_closed || m_stopped);
 }
 
 void RTCPeerConnection::createOffer(RTCSessionDescriptionCallback* successCallback, RTCErrorCallback* errorCallback, const Dictionary& rtcOfferOptions, ExceptionState& exceptionState)
@@ skipping 47 matching lines @@
 
     RTCVoidRequest* request = RTCVoidRequestImpl::create(executionContext(), this, successCallback, errorCallback);
     m_peerHandler->setLocalDescription(request, sessionDescription->webSessionDescription());
 }
 
 RTCSessionDescription* RTCPeerConnection::localDescription(ExceptionState& exceptionState)
 {
     WebRTCSessionDescription webSessionDescription = m_peerHandler->localDescription();
     if (webSessionDescription.isNull())
         return nullptr;
-
-    return RTCSessionDescription::create(webSessionDescription);
+    m_localDescription->setWebSessionDescription(webSessionDescription);

[Jens Widell, 2015/04/28 10:59:22]

I think the semantics might be somewhat incorrect here (and in
setLocalDescription() + same for remote).

I don't know what might make the description change (since I don't know WebRTC
at all) but if it were to change, it seems more reasonable to return a new
RTCSessionDescription object, instead of mutating the one we have, and might
have returned earlier.

The spec definitely says to return the last description successfully via
setLocalDescription(), which implies that setLocalDescription() should make this
setter later return a different object. That is, that setLocalDescription()
should simply store the description argument in m_localDescription so that we
can return it later.

And then we should perhaps have an update mechanism here so that if we have an
existing description in m_localDescription but what
m_peerHandler->localDescription() returns doesn't match it, that we create a new
RTCSessionDescription object with that information and store it in
m_localDescription.

This is all somewhat complicated though by the fact that RTCSessionDescription
objects aren't immutable, meaning whatever description we return to the script
(or that a script sets via setLocalDescription()) could later be modified
directly by the script, which the specification doesn't mention (or at least not
where I'd expect to find it mentioned.)

+    return m_localDescription;
 }
 
 void RTCPeerConnection::setRemoteDescription(RTCSessionDescription* sessionDescription, VoidCallback* successCallback, RTCErrorCallback* errorCallback, ExceptionState& exceptionState)
 {
     if (throwExceptionIfSignalingStateClosed(m_signalingState, exceptionState))
         return;
 
     if (!sessionDescription) {
         exceptionState.throwDOMException(TypeMismatchError, ExceptionMessages::argumentNullOrIncorrectType(1, "RTCSessionDescription"));
         return;
     }
 
     RTCVoidRequest* request = RTCVoidRequestImpl::create(executionContext(), this, successCallback, errorCallback);
     m_peerHandler->setRemoteDescription(request, sessionDescription->webSessionDescription());
 }
 
 RTCSessionDescription* RTCPeerConnection::remoteDescription(ExceptionState& exceptionState)
 {
     WebRTCSessionDescription webSessionDescription = m_peerHandler->remoteDescription();
     if (webSessionDescription.isNull())
         return nullptr;
+    m_remoteDescription->setWebSessionDescription(webSessionDescription);
 
-    return RTCSessionDescription::create(webSessionDescription);
+    return m_remoteDescription;
 }
 
 void RTCPeerConnection::updateIce(const Dictionary& rtcConfiguration, const Dictionary& mediaConstraints, ExceptionState& exceptionState)
 {
     if (throwExceptionIfSignalingStateClosed(m_signalingState, exceptionState))
         return;
 
     RTCConfiguration* configuration = parseConfiguration(rtcConfiguration, exceptionState);
     if (exceptionState.hadException())
         return;
@@ skipping 375 matching lines @@
     m_iceConnectionState = ICEConnectionStateClosed;
     m_signalingState = SignalingStateClosed;
 
     HeapVector<Member<RTCDataChannel>>::iterator i = m_dataChannels.begin();
     for (; i != m_dataChannels.end(); ++i)
         (*i)->stop();
     m_dataChannels.clear();
 
     m_dispatchScheduledEventRunner.stop();
 
+    m_localDescription->stop();
+    m_remoteDescription->stop();
+
     m_peerHandler.clear();
 }
 
 void RTCPeerConnection::changeSignalingState(SignalingState signalingState)
 {
     if (m_signalingState != SignalingStateClosed && m_signalingState != signalingState) {
         m_signalingState = signalingState;
         scheduleDispatchEvent(Event::create(EventTypeNames::signalingstatechange));
     }
 }
@@ skipping 42 matching lines @@
         dispatchEvent((*it).release());
 
     events.clear();
 }
 
 DEFINE_TRACE(RTCPeerConnection)
 {
     visitor->trace(m_localStreams);
     visitor->trace(m_remoteStreams);
     visitor->trace(m_dataChannels);
+    visitor->trace(m_localDescription);
+    visitor->trace(m_remoteDescription);
 #if ENABLE(OILPAN)
     visitor->trace(m_scheduledEvents);
 #endif
     RefCountedGarbageCollectedEventTargetWithInlineData<RTCPeerConnection>::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink