MojoCompositorFrameSinkPrivate should support copy requests

cc/ipc/mojo_compositor_frame_sink.mojom

Index: cc/ipc/mojo_compositor_frame_sink.mojom
diff --git a/cc/ipc/mojo_compositor_frame_sink.mojom b/cc/ipc/mojo_compositor_frame_sink.mojom
index bf2e196f79956523a6f3e578a2decc796cd35959..98194434b0c9d9de6c00ec147b505a42c84acee6 100644
--- a/cc/ipc/mojo_compositor_frame_sink.mojom
+++ b/cc/ipc/mojo_compositor_frame_sink.mojom
@@ -6,11 +6,15 @@ module cc.mojom;
 
 import "cc/ipc/begin_frame_args.mojom";
 import "cc/ipc/compositor_frame.mojom";
+import "cc/ipc/copy_output_request.mojom";
+import "cc/ipc/copy_output_result.mojom";
 import "cc/ipc/frame_sink_id.mojom";
 import "cc/ipc/local_surface_id.mojom";
 import "cc/ipc/surface_reference.mojom";
 import "cc/ipc/returned_resource.mojom";
 import "cc/ipc/surface_sequence.mojom";
+import "gpu/ipc/common/mailbox.mojom";
+import "gpu/ipc/common/sync_token.mojom";
 
 // A MojoCompositorFrameSink is an interface for receiving CompositorFrame
 // structs. A CompositorFrame contains the complete output meant for display.
@@ -47,6 +51,11 @@ interface MojoCompositorFrameSink {
   // Mark the sequence as satisfied and garbage collect surfaces.
   Satisfy(cc.mojom.SurfaceSequence sequence);
 
+  RequestCopyOfSurface(cc.mojom.CopyOutputRequest request)
+      => (cc.mojom.CopyOutputResult result);
+
+  DeleteMailbox(gpu.mojom.Mailbox mailbox, gpu.mojom.SyncToken sync_token, bool is_lost);

[Fady Samuel, 2017/02/06 17:13:48]

This is way too generic, in my opinion. Why do we need this?

[danakj, 2017/02/06 19:18:51]

Same, CFS can transport resources but it doesn't manage lifetimes. Textures are
deleted/mailboxes are dereffed thru a GL context.

[Fady Samuel, 2017/02/06 19:45:02]

This sync token indicates when it's safe to delete this mailbox, right? Can The
display compositor allocate the synctoken instead and pass it to the client in
CopyOutputResult?

[Saman Sami, 2017/02/06 20:04:00]

Can you explain how it should be? I'm basically trying to mimic how copy
requests work at the moment. The requester has to run a callback to delete the
mailbox (called release_callback_ in CopyOutputResult). Since the callback would
be tricky with mojo, I added a method to the mojo interface which acts like that
callback.

[danakj, 2017/02/06 20:09:15]

I see, just call this ReleaseMailbox then. It doesn't delete, it tells the
service that it is done with it and is releasing ownership of its contents.
Delete implies something else altogether and may be what the service does, or
not.

[danakj, 2017/02/06 20:10:27]

ReleaseMailboxForCopyOutputResult might work too if that is too general as this
is a widely used API. Or can the cc.mojom.CopyOutputResult provide this somehow
to namespace it?

+
   // TODO(fsamuel): ReadbackBitmap API would be useful here.

[Fady Samuel, 2017/02/06 17:13:49]

Delete this?

 };