Implements ListenForSessionMessages in PresentationServiceImpl; uses Swap to avoid copying large da…

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 c07f2658e2a5b2bc045bee6a321cf72bc256df5e..50759293cf7973ce2f82bc0774984896143535e6 100644
--- a/content/renderer/presentation/presentation_dispatcher.cc
+++ b/content/renderer/presentation/presentation_dispatcher.cc
@@ -213,7 +213,8 @@ void PresentationDispatcher::OnSessionStateChange(
 
 void PresentationDispatcher::OnSessionMessagesReceived(
     mojo::Array<presentation::SessionMessagePtr> messages) {
-  if (!controller_)
+  // When messages is null, there is an error at presentation service side.
+  if (!controller_ || messages.is_null())
     return;
 
   for (size_t i = 0; i < messages.size(); ++i) {