Fix issue of localDescription and remoteDescription getter.

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 51a5d99241a3b761e296aeab803183121f94da90..b91c40dfce8e8317a49b8c44d8ddd87d7c42be80 100644
--- a/Source/modules/mediastream/RTCPeerConnection.cpp
+++ b/Source/modules/mediastream/RTCPeerConnection.cpp
@@ -241,6 +241,8 @@ RTCPeerConnection* RTCPeerConnection::create(ExecutionContext* context, const Di
 
 RTCPeerConnection::RTCPeerConnection(ExecutionContext* context, RTCConfiguration* configuration, WebMediaConstraints constraints, ExceptionState& exceptionState)
     : ActiveDOMObject(context)
+    , m_pendingLocalDescription(nullptr)
+    , m_pendingRemoteDescription(nullptr)
     , m_signalingState(SignalingStateStable)
     , m_iceGatheringState(ICEGatheringStateNew)
     , m_iceConnectionState(ICEConnectionStateNew)
@@ -275,6 +277,8 @@ RTCPeerConnection::RTCPeerConnection(ExecutionContext* context, RTCConfiguration
         exceptionState.throwDOMException(NotSupportedError, "Failed to initialize native PeerConnection.");
         return;
     }
+    m_localDescription = RTCSessionDescription::create(m_peerHandler->localDescription());
+    m_remoteDescription = RTCSessionDescription::create(m_peerHandler->remoteDescription());
 }
 
 RTCPeerConnection::~RTCPeerConnection()
@@ -335,15 +339,16 @@ void RTCPeerConnection::setLocalDescription(RTCSessionDescription* sessionDescri
 
     RTCVoidRequest* request = RTCVoidRequestImpl::create(executionContext(), this, successCallback, errorCallback);
     m_peerHandler->setLocalDescription(request, sessionDescription->webSessionDescription());
+    m_pendingLocalDescription = sessionDescription;
 }
 
-RTCSessionDescription* RTCPeerConnection::localDescription(ExceptionState& exceptionState)
+RTCSessionDescription* RTCPeerConnection::localDescription()
 {
-    WebRTCSessionDescription webSessionDescription = m_peerHandler->localDescription();
-    if (webSessionDescription.isNull())
+    if (!m_peerHandler || m_peerHandler->localDescription().isNull())
         return nullptr;
 
-    return RTCSessionDescription::create(webSessionDescription);
+    updateLocalSessionDescriptionIfNeeded(false);
+    return m_localDescription;
 }
 
 void RTCPeerConnection::setRemoteDescription(RTCSessionDescription* sessionDescription, VoidCallback* successCallback, RTCErrorCallback* errorCallback, ExceptionState& exceptionState)
@@ -358,15 +363,16 @@ void RTCPeerConnection::setRemoteDescription(RTCSessionDescription* sessionDescr
 
     RTCVoidRequest* request = RTCVoidRequestImpl::create(executionContext(), this, successCallback, errorCallback);
     m_peerHandler->setRemoteDescription(request, sessionDescription->webSessionDescription());
+    m_pendingRemoteDescription = sessionDescription;
 }
 
-RTCSessionDescription* RTCPeerConnection::remoteDescription(ExceptionState& exceptionState)
+RTCSessionDescription* RTCPeerConnection::remoteDescription()
 {
-    WebRTCSessionDescription webSessionDescription = m_peerHandler->remoteDescription();
-    if (webSessionDescription.isNull())
+    if (!m_peerHandler || m_peerHandler->remoteDescription().isNull())
         return nullptr;
 
-    return RTCSessionDescription::create(webSessionDescription);
+    updateRemoteSessionDescriptionIfNeeded(false);
+    return m_remoteDescription;
 }
 
 void RTCPeerConnection::updateIce(const Dictionary& rtcConfiguration, const Dictionary& mediaConstraints, ExceptionState& exceptionState)
@@ -627,6 +633,44 @@ void RTCPeerConnection::close(ExceptionState& exceptionState)
     closeInternal();
 }
 
+void RTCPeerConnection::updateLocalSessionDescriptionIfNeeded(bool pending)
+{
+    if (!m_peerHandler)
+        return;
+    WebRTCSessionDescription webSessionDescription = m_peerHandler->localDescription();
+    if (webSessionDescription.isNull())
+        return;
+
+    if (pending) {

[Jens Widell, 2015/05/05 06:31:20]

This code path has essentially nothing in common with the rest of the function,
so I'd just make this bit its own (very simple) function, called
commitPendingLocalSessionDescription() or something like that.

[changbin, 2015/05/05 07:02:29]

Therefore, your proposal would be,
1. Move out 'if(pending)' logic into a separate function, named
commitPendingLocalSessionDescription().
2. Move updateLocalSessionDescriptionIfNeeded() codes back in localDescription()
getter.
3. In RTCVoidRequestImpl::requestSucceeded(), call
commitPendingLocalSessionDescription().

Is my understanding correct? 

[Jens Widell, 2015/05/05 07:17:21]

Correct.

Though 2 is somewhat optional. Keeping this helper might make sense simply for
the purpose of having a function name that documents what's going on. Or not. I
have no strong opinion. :-)

+        m_localDescription = m_pendingLocalDescription;
+        return;
+    }
+
+    if (!m_localDescription || m_localDescription->webSessionDescription().isNull()
+        || m_localDescription->webSessionDescription() != webSessionDescription) {
+        m_localDescription = RTCSessionDescription::create(webSessionDescription);
+    }
+}
+
+void RTCPeerConnection::updateRemoteSessionDescriptionIfNeeded(bool pending)
+{
+    if (!m_peerHandler)
+        return;
+    WebRTCSessionDescription webSessionDescription = m_peerHandler->remoteDescription();
+    if (webSessionDescription.isNull())
+        return;
+
+    if (pending) {
+        m_remoteDescription = m_pendingRemoteDescription;
+        return;
+    }
+
+    if (!m_remoteDescription || m_remoteDescription->webSessionDescription().isNull()
+        || m_remoteDescription->webSessionDescription() != webSessionDescription) {
+        m_remoteDescription = RTCSessionDescription::create(webSessionDescription);
+    }
+}
+
 void RTCPeerConnection::negotiationNeeded()
 {
     ASSERT(!m_closed);
@@ -824,6 +868,10 @@ DEFINE_TRACE(RTCPeerConnection)
     visitor->trace(m_localStreams);
     visitor->trace(m_remoteStreams);
     visitor->trace(m_dataChannels);
+    visitor->trace(m_localDescription);
+    visitor->trace(m_remoteDescription);
+    visitor->trace(m_pendingLocalDescription);
+    visitor->trace(m_pendingRemoteDescription);
 #if ENABLE(OILPAN)
     visitor->trace(m_scheduledEvents);
 #endif