[PresentationAPI] Ensures only one pending message callback at a time if a frame created multiple s…

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 6691be68207d752afcfe8c499db8a2098a000cab..ac4dbb768fbd963e2b6c3d4152e0cdd84a9387ee 100644
--- a/content/renderer/presentation/presentation_dispatcher.cc
+++ b/content/renderer/presentation/presentation_dispatcher.cc
@@ -83,7 +83,8 @@ PresentationDispatcher::PresentationDispatcher(RenderFrame* render_frame)
       controller_(nullptr),
       binding_(this),
       listening_state_(ListeningState::Inactive),
-      last_known_availability_(false) {
+      last_known_availability_(false),
+      listening_for_messages_(false) {
 }
 
 PresentationDispatcher::~PresentationDispatcher() {
@@ -337,6 +338,8 @@ void PresentationDispatcher::DidCommitProvisionalLoad(
   // Remove all pending send message requests.
   MessageRequestQueue empty;
   std::swap(message_request_queue_, empty);
+
+  listening_for_messages_ = false;
 }
 
 void PresentationDispatcher::OnScreenAvailabilityUpdated(bool available) {
@@ -370,6 +373,7 @@ void PresentationDispatcher::OnDefaultSessionStarted(
   if (!session_info.is_null()) {
     controller_->didStartDefaultSession(
         new PresentationSessionClient(session_info.Pass()));
+    StartListenForMessages();
   }
 }
 
@@ -388,6 +392,14 @@ void PresentationDispatcher::OnSessionCreated(
 
   DCHECK(!session_info.is_null());
   callback->onSuccess(new PresentationSessionClient(session_info.Pass()));
+  StartListenForMessages();
+}
+
+void PresentationDispatcher::StartListenForMessages() {
+  if (listening_for_messages_)
+    return;
+
+  listening_for_messages_ = true;
   presentation_service_->ListenForSessionMessages(
       base::Bind(&PresentationDispatcher::OnSessionMessagesReceived,
                  base::Unretained(this)));
@@ -411,9 +423,14 @@ void PresentationDispatcher::OnSessionStateChange(
 
 void PresentationDispatcher::OnSessionMessagesReceived(
     mojo::Array<presentation::SessionMessagePtr> messages) {
+  if (!listening_for_messages_)

[Kevin M, 2015/07/08 20:16:08]

Add a LOG/DLOG here to call our attention to strange behavior.

[haibinlu, 2015/07/08 20:47:41]

added comments.

this may happen. frame navigated, and MR sent last batches of messages; where
there may be race condition.

+    return;
+
   // When messages is null, there is an error at presentation service side.
-  if (!controller_ || messages.is_null())
+  if (!controller_ || messages.is_null()) {
+    listening_for_messages_ = false;

[Kevin M, 2015/07/08 20:16:07]

LOG?

[haibinlu, 2015/07/08 20:47:41]

null message is expected to indicate messaging error or the end of messaging
channel due to route removal. Log is not really necessary.

     return;
+  }
 
   for (size_t i = 0; i < messages.size(); ++i) {
     if (messages[i]->type ==