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(m_peerHandler->localDescription());
+    m_remoteDescription = RTCSessionDescription::create(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 40 matching lines @@
     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->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)
 {
     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());
+    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)
 {
     if (throwExceptionIfSignalingStateClosed(m_signalingState, exceptionState))
         return;
 
     RTCConfiguration* configuration = parseConfiguration(rtcConfiguration, exceptionState);
     if (exceptionState.hadException())
         return;
@@ skipping 437 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