[PresentationAPI] Added on-session-text-message handler.

Source/modules/presentation/Presentation.cpp

Index: Source/modules/presentation/Presentation.cpp
diff --git a/Source/modules/presentation/Presentation.cpp b/Source/modules/presentation/Presentation.cpp
index 4c6ddaebe1a6e9815b73600a290024e1a6cec557..6ef6307c8934a53802f313219dcca8a74892fc89 100644
--- a/Source/modules/presentation/Presentation.cpp
+++ b/Source/modules/presentation/Presentation.cpp
@@ -161,6 +161,15 @@ void Presentation::didChangeSessionState(WebPresentationSessionClient* sessionCl
     PresentationSession::dispose(sessionClient);
 }
 
+void Presentation::didReceiveSessionTextMessage(WebPresentationSessionClient* sessionClient, const String& message)
+{
+    PresentationSession* session = findSession(sessionClient);
+    if (session)
+        session->didReceiveTextMessage(message);
+
+    PresentationSession::dispose(sessionClient);
+}
+
 void Presentation::registerSession(PresentationSession* session)
 {
     m_openSessions.add(session);