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

content/browser/presentation/presentation_service_impl.cc

Index: content/browser/presentation/presentation_service_impl.cc
diff --git a/content/browser/presentation/presentation_service_impl.cc b/content/browser/presentation/presentation_service_impl.cc
index 19372a179473915a2e2c95a9b68e0f1dbe60b03e..3845c3bf9f06bf5365f9a3a11b8cf005b19b0c02 100644
--- a/content/browser/presentation/presentation_service_impl.cc
+++ b/content/browser/presentation/presentation_service_impl.cc
@@ -10,6 +10,7 @@
 #include "content/browser/presentation/presentation_type_converters.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/navigation_details.h"
+#include "content/public/browser/presentation_session_message.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/web_contents.h"
@@ -335,7 +336,47 @@ bool PresentationServiceImpl::FrameMatches(
 
 void PresentationServiceImpl::ListenForSessionMessages(
     const SessionMessagesCallback& callback) {
-  NOTIMPLEMENTED();
+  DVLOG(2) << "ListenForSessionMessages";
+  if (!delegate_) {
+    callback.Run(mojo::Array<presentation::SessionMessagePtr>());
+    return;
+  }
+
+  delegate_->ListenForSessionMessages(
+      render_process_id_, render_frame_id_,
+      base::Bind(&PresentationServiceImpl::OnSessionMessages,
+                 weak_factory_.GetWeakPtr(), callback));

[imcheng (use chromium acct), 2015/04/30 21:52:01]

I am not sure about binding the mojo callback to OnSessionMessages. There is no
guarantee when OnSessionMessages will be invoked and by that time the onmessage
handler could already be gone. (or page navigated, etc.)

One possible approach is to store callback as a scoped_ptr<> in
PresentationServiceImpl and then invoke it when OnSessionMessages comes back.
That way we can also invoke the callback and then reset the ptr on Reset()
(which is called on navigation and frame deletion)

[haibinlu, 2015/05/01 01:37:11]

Done.

+}
+
+void PresentationServiceImpl::OnSessionMessages(
+    const SessionMessagesCallback& callback,
+    scoped_ptr<ScopedVector<PresentationSessionMessage>> messages) {

[imcheng (use chromium acct), 2015/04/30 21:52:01]

should probably add a DCHECK on messages

[haibinlu, 2015/05/01 19:03:19]

Done.

+  mojo::Array<presentation::SessionMessagePtr> mojoMessages(messages->size());
+  for (size_t i = 0; i < messages->size(); ++i)
+    mojoMessages[i] = PresentationServiceImpl::ToMojoSessionMessage(
+        messages.get()->get().at(i));
+
+  callback.Run(mojoMessages.Pass());
+}
+
+// static
+presentation::SessionMessagePtr PresentationServiceImpl::ToMojoSessionMessage(
+    PresentationSessionMessage* input) {
+  presentation::SessionMessagePtr output(presentation::SessionMessage::New());
+  output->presentation_url = input->presentation_url;
+  output->presentation_id = input->presentation_id;
+  if (input->message->size() == 0) {
+    // binary data
+    output->type = presentation::PresentationMessageType::
+        PRESENTATION_MESSAGE_TYPE_ARRAY_BUFFER;
+    output->data.Swap(input->data.get());
+  } else {
+    // string message
+    output->type =
+        presentation::PresentationMessageType::PRESENTATION_MESSAGE_TYPE_TEXT;
+    output->message.Swap(input->message.get());
+  }
+  return output.Pass();
 }
 
 void PresentationServiceImpl::DidNavigateAnyFrame(