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

Source/modules/presentation/PresentationController.cpp

Index: Source/modules/presentation/PresentationController.cpp
diff --git a/Source/modules/presentation/PresentationController.cpp b/Source/modules/presentation/PresentationController.cpp
index 8021fe24fd710b3bfcf35b8a8888ee8d730707ed..47c7f1bbc9a9b33cba07d5fca2b2ad93b5c3aac8 100644
--- a/Source/modules/presentation/PresentationController.cpp
+++ b/Source/modules/presentation/PresentationController.cpp
@@ -94,6 +94,14 @@ void PresentationController::didChangeSessionState(WebPresentationSessionClient*
         PresentationSession::dispose(sessionClient);
 }
 
+void PresentationController::didReceiveSessionTextMessage(WebPresentationSessionClient* sessionClient, const WebString& message)
+{
+    if (m_presentation)
+        m_presentation->didReceiveSessionTextMessage(sessionClient, message);
+    else
+        PresentationSession::dispose(sessionClient);
+}
+
 void PresentationController::startSession(const String& presentationUrl, const String& presentationId, WebPresentationSessionClientCallbacks* callbacks)
 {
     if (!m_client) {