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..54d847684b922b40a6e12e7ddca4190ed554134b 100644
--- a/Source/modules/mediastream/RTCPeerConnection.cpp
+++ b/Source/modules/mediastream/RTCPeerConnection.cpp
@@ -275,6 +275,8 @@ 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 +337,21 @@ void RTCPeerConnection::setLocalDescription(RTCSessionDescription* sessionDescri
 
     RTCVoidRequest* request = RTCVoidRequestImpl::create(executionContext(), this, successCallback, errorCallback);
     m_peerHandler->setLocalDescription(request, sessionDescription->webSessionDescription());
+    m_localDescription = sessionDescription;
 }
 
-RTCSessionDescription* RTCPeerConnection::localDescription(ExceptionState& exceptionState)
+RTCSessionDescription* RTCPeerConnection::localDescription()
 {
+    if (!m_peerHandler)
+        return nullptr;
     WebRTCSessionDescription webSessionDescription = m_peerHandler->localDescription();
     if (webSessionDescription.isNull())
         return nullptr;
 
-    return RTCSessionDescription::create(webSessionDescription);
+    if (!m_localDescription || m_localDescription->webSessionDescription() != webSessionDescription) {
+        m_localDescription = RTCSessionDescription::create(webSessionDescription);
+    }
+    return m_localDescription;
 }
 
 void RTCPeerConnection::setRemoteDescription(RTCSessionDescription* sessionDescription, VoidCallback* successCallback, RTCErrorCallback* errorCallback, ExceptionState& exceptionState)
@@ -358,15 +366,21 @@ void RTCPeerConnection::setRemoteDescription(RTCSessionDescription* sessionDescr
 
     RTCVoidRequest* request = RTCVoidRequestImpl::create(executionContext(), this, successCallback, errorCallback);
     m_peerHandler->setRemoteDescription(request, sessionDescription->webSessionDescription());
+    m_remoteDescription = sessionDescription;

[Jens Widell, 2015/05/04 06:44:23]

I'm unsure exactly how things work here, but I suspect it would be more correct
to delay this setting (and the one in setLocalDescription()) to when
RTCVoidRequestImpl::requestSucceeded() is called.

[changbin, 2015/05/04 10:12:23]

Agree and thanks:)
Current implemention will give a wrong value for m_remoteDescription if peer
handler fails to set inside. Though it's fixed by the remoteDescription getter
function.

[Jens Widell, 2015/05/04 10:20:50]

Now you no longer keep the object passed to setRemoteDescription(). My reading
of the specification is that the getter should return that actual object (once
successfully set), rather than an object identical to it.

You could store it in an m_pendingRemoteDescription here and then move that over
to m_remoteDescription once the description has been updated successfully.

But really, an owner of this code should comment on these details, instead of
me.

 }
 
-RTCSessionDescription* RTCPeerConnection::remoteDescription(ExceptionState& exceptionState)
+RTCSessionDescription* RTCPeerConnection::remoteDescription()
 {
+    if (!m_peerHandler)
+        return nullptr;
     WebRTCSessionDescription webSessionDescription = m_peerHandler->remoteDescription();
     if (webSessionDescription.isNull())
         return nullptr;
 
-    return RTCSessionDescription::create(webSessionDescription);
+    if (!m_remoteDescription || m_remoteDescription->webSessionDescription() != webSessionDescription) {
+        m_remoteDescription = RTCSessionDescription::create(webSessionDescription);
+    }
+    return m_remoteDescription;
 }
 
 void RTCPeerConnection::updateIce(const Dictionary& rtcConfiguration, const Dictionary& mediaConstraints, ExceptionState& exceptionState)
@@ -824,6 +838,8 @@ 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