Send FrameSwapMessageQueue's messages with a separate IPC

content/renderer/gpu/renderer_compositor_frame_sink.cc

Index: content/renderer/gpu/renderer_compositor_frame_sink.cc
diff --git a/content/renderer/gpu/renderer_compositor_frame_sink.cc b/content/renderer/gpu/renderer_compositor_frame_sink.cc
index 39d110095b06863794d33c8741f0854a801c16eb..007372bdc031d5554b91410ee2261de81bec3c7a 100644
--- a/content/renderer/gpu/renderer_compositor_frame_sink.cc
+++ b/content/renderer/gpu/renderer_compositor_frame_sink.cc
@@ -49,7 +49,8 @@ RendererCompositorFrameSink::RendererCompositorFrameSink(
           synthetic_begin_frame_source_
               ? nullptr
               : base::MakeUnique<cc::ExternalBeginFrameSource>(this)),
-      routing_id_(routing_id) {
+      routing_id_(routing_id),
+      last_used_frame_token_(compositor_frame_sink_id << 28) {

[Fady Samuel, 2017/03/31 16:45:14]

I'd rather FrameToken be a struct with two ints like FrameSinkId instead of a
single int with a bunch of bit shifting.. It's easier to read and understand
that way.

[Saman Sami, 2017/04/03 19:22:28]

What should those two ints be called? Frame token is a general-purpose token
that any two parent / child should be able to use. I'm afraid that we might make
it too browser/renderer-specific by splitting it into two ints because that's
renderer's implementation to some extent.

   DCHECK(compositor_frame_sink_filter_);
   DCHECK(frame_swap_message_queue_);
   DCHECK(message_sender_);
@@ -73,7 +74,8 @@ RendererCompositorFrameSink::RendererCompositorFrameSink(
           synthetic_begin_frame_source_
               ? nullptr
               : base::MakeUnique<cc::ExternalBeginFrameSource>(this)),
-      routing_id_(routing_id) {
+      routing_id_(routing_id),
+      last_used_frame_token_(compositor_frame_sink_id << 28) {
   DCHECK(compositor_frame_sink_filter_);
   DCHECK(frame_swap_message_queue_);
   DCHECK(message_sender_);
@@ -130,18 +132,27 @@ void RendererCompositorFrameSink::SubmitCompositorFrame(
   if (ShouldAllocateNewLocalSurfaceId(frame))
     local_surface_id_ = id_allocator_.GenerateId();
   UpdateFrameData(frame);
+
   {
     std::unique_ptr<FrameSwapMessageQueue::SendMessageScope>
         send_message_scope =
             frame_swap_message_queue_->AcquireSendMessageScope();
     std::vector<std::unique_ptr<IPC::Message>> messages;
-    std::vector<IPC::Message> messages_to_deliver_with_frame;
     frame_swap_message_queue_->DrainMessages(&messages);
-    FrameSwapMessageQueue::TransferMessages(&messages,
-                                            &messages_to_deliver_with_frame);
-    Send(new ViewHostMsg_SwapCompositorFrame(
-        routing_id_, compositor_frame_sink_id_, local_surface_id_, frame,
-        messages_to_deliver_with_frame));
+    std::vector<IPC::Message> messages_to_send;
+    std::vector<IPC::Message> dummy;
+    FrameSwapMessageQueue::TransferMessages(&messages, &messages_to_send);
+    uint32_t frame_token = 0;
+    if (!messages_to_send.empty())
+      frame_token = ++last_used_frame_token_;
+    frame.metadata.frame_token = frame_token;
+    Send(new ViewHostMsg_SwapCompositorFrame(routing_id_,
+                                             compositor_frame_sink_id_,
+                                             local_surface_id_, frame, dummy));
+    if (frame_token) {
+      Send(new ViewHostMsg_FrameSwapMessages(routing_id_, frame_token,
+                                             messages_to_send));
+    }
     // ~send_message_scope.
   }
 }