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

content/browser/presentation/presentation_service_impl.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_PRESENTATION_PRESENTATION_SERVICE_IMPL_H_
 #define CONTENT_BROWSER_PRESENTATION_PRESENTATION_SERVICE_IMPL_H_
 
 #include <deque>
 
 #include "base/basictypes.h"
@@ skipping 10 matching lines @@
 #include "content/public/browser/navigation_details.h"
 #include "content/public/browser/presentation_screen_availability_listener.h"
 #include "content/public/browser/presentation_service_delegate.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/common/frame_navigate_params.h"
 
 namespace content {
 
 struct FrameNavigateParams;
 struct LoadCommittedDetails;
+struct PresentationSessionMessage;
 class RenderFrameHost;
 
 // Implementation of Mojo PresentationService.
 // It handles Presentation API requests coming from Blink / renderer process
 // and delegates the requests to the embedder's media router via
 // PresentationServiceDelegate.
 // An instance of this class tied to a RenderFrameHost and listens to events
 // related to the RFH via implementing WebContentsObserver.
 // This class is instantiated on-demand via Mojo's ConnectToRemoteService
 // from the renderer when the first presentation API request is handled.
@@ skipping 219 matching lines @@
       bool is_start_session,
       int request_session_id,
       const PresentationError& error);
 
   // Requests delegate to start a session.
   void DoStartSession(
       const std::string& presentation_url,
       const std::string& presentation_id,
       const NewSessionMojoCallback& callback);
 
+  void OnSessionMessages(

[whywhat, 2015/05/01 15:26:12]

Please, document that for optimization purposes, this method will empty the
messages passed to it.
On the related note, do we know if copying the messages would be so bad? How
often to pages send messages and how big the payload typically is?

[haibinlu, 2015/05/01 19:03:20]

Done. Message size is up to 64KB. With get-next-batch-message pattern, messages
will be sent as fast as blink+MR can handle. With copying, each message will be
copied at least 4 times along the way, one per each end of the two mojo pipes
when converting to/from mojo message struct type.

+      scoped_ptr<ScopedVector<PresentationSessionMessage>> messages);
+
+  static presentation::SessionMessagePtr ToMojoSessionMessage(

[whywhat, 2015/05/01 15:26:12]

move to the .cc file and the unnamed namespace? doesn't have to be a class
member.

[haibinlu, 2015/05/01 19:03:20]

Done.

+      content::PresentationSessionMessage* input);
+
   // Removes the head of the queue (which represents the request that has just
   // been processed).
   // Checks if there are any queued StartSession requests and if so, executes
   // the first one in the queue.
   void HandleQueuedStartSessionRequests();
 
   // Associates |callback| with a unique request ID and stores it in a map.
   int RegisterNewSessionCallback(
     const NewSessionMojoCallback& callback);
 
@@ skipping 31 matching lines @@
 
   int next_request_session_id_;
   base::hash_map<int, linked_ptr<NewSessionMojoCallback>> pending_session_cbs_;
 
   scoped_ptr<DefaultSessionStartContext> default_session_start_context_;
 
   // RAII binding of |this| to an Presentation interface request.
   // The binding is removed when binding_ is cleared or goes out of scope.
   scoped_ptr<mojo::Binding<presentation::PresentationService>> binding_;
 
+  scoped_ptr<SessionMessagesCallback> on_session_messages_;

[whywhat, 2015/05/01 15:26:12]

nit: postfix the name with callback_. without knowing the type this looks like a
vector of messages, not a callback.

[haibinlu, 2015/05/01 19:03:20]

Done.

+
   // ID of the RenderFrameHost this object is associated with.
   int render_process_id_;
   int render_frame_id_;
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<PresentationServiceImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PresentationServiceImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_PRESENTATION_PRESENTATION_SERVICE_IMPL_H_