[PresentationAPI] Added on-session-message handler.

content/renderer/presentation/presentation_dispatcher.cc

Index: content/renderer/presentation/presentation_dispatcher.cc
diff --git a/content/renderer/presentation/presentation_dispatcher.cc b/content/renderer/presentation/presentation_dispatcher.cc
index 39e5238b189b9fd7c3219337565554affc628c92..59cfa74cdb1610bdffa506541d64e3cf0e21425d 100644
--- a/content/renderer/presentation/presentation_dispatcher.cc
+++ b/content/renderer/presentation/presentation_dispatcher.cc
@@ -210,6 +210,22 @@ void PresentationDispatcher::OnSessionStateChange(
       GetWebPresentationSessionStateFromMojo(session_state));
 }
 
+void PresentationDispatcher::OnSessionTextMessageReceived(
+    presentation::PresentationSessionInfoPtr session_info,
+    const std::string& message) {
+  if (!controller_)
+    return;
+
+  presentation_service_->ListenForSessionTextMessage(base::Bind(
+      &PresentationDispatcher::OnSessionTextMessageReceived,
+      base::Unretained(this)));
+
+  DCHECK(!session_info.is_null());
+  controller_->didReceiveSessionTextMessage(
+      new PresentationSessionClient(session_info.Pass()),
+      blink::WebString::fromUTF8(message));
+}
+
 void PresentationDispatcher::ConnectToPresentationServiceIfNeeded() {
   if (presentation_service_.get())
     return;
@@ -225,6 +241,9 @@ void PresentationDispatcher::ConnectToPresentationServiceIfNeeded() {
   presentation_service_->ListenForSessionStateChange(base::Bind(
       &PresentationDispatcher::OnSessionStateChange,
       base::Unretained(this)));
+  presentation_service_->ListenForSessionTextMessage(base::Bind(
+      &PresentationDispatcher::OnSessionTextMessageReceived,
+      base::Unretained(this)));
   */
 }