MojoCompositorFrameSinkPrivate should support copy requests

cc/surfaces/compositor_frame_sink_support.cc

Index: cc/surfaces/compositor_frame_sink_support.cc
diff --git a/cc/surfaces/compositor_frame_sink_support.cc b/cc/surfaces/compositor_frame_sink_support.cc
index 95222ed1defc2354e69faf20ac12300a4b439b61..4887b71d916a4e8aff3e8b2a208e2cab9603d2f3 100644
--- a/cc/surfaces/compositor_frame_sink_support.cc
+++ b/cc/surfaces/compositor_frame_sink_support.cc
@@ -179,4 +179,34 @@ void CompositorFrameSinkSupport::UpdateNeedsBeginFramesInternal() {
     begin_frame_source_->RemoveObserver(this);
 }
 
+void CompositorFrameSinkSupport::RequestCopyOfSurface(
+    std::unique_ptr<CopyOutputRequest> request) {
+  request->set_result_callback(
+      base::Bind(&CompositorFrameSinkSupport::OnTextureReceived,
+                 weak_factory_.GetWeakPtr(), request->result_callback()));
+  surface_factory_.RequestCopyOfSurface(std::move(request));
+}
+
+void CompositorFrameSinkSupport::ReleaseCopyOfSurface(
+    const gpu::Mailbox& mailbox,
+    const gpu::SyncToken& sync_token,
+    bool is_lost) {
+  auto callback_iter = release_callbacks_.find(mailbox);
+  if (!release_callbacks_.count(mailbox)) {
+    DLOG(ERROR) << "Attempted to delete a mailbox that does not exist";
+    return;
+  }
+  callback_iter->second->Run(sync_token, is_lost);
+  release_callbacks_.erase(callback_iter);
+}
+
+void CompositorFrameSinkSupport::OnTextureReceived(
+    CopyOutputRequest::CopyOutputRequestCallback callback,
+    std::unique_ptr<CopyOutputResult> result) {
+  DCHECK(result->HasTexture());
+  DCHECK(!release_callbacks_.count(result->mailbox()));
+  release_callbacks_[result->mailbox()] = result->TakeReleaseCallback();
+  callback.Run(std::move(result));

[danakj, 2017/02/06 23:02:12]

The result here should have a release callback to calls to ReleaseCopyOfSurface.
It looks like you want a CreateRelayResult similar to CreateRelayRequest? It can
move the contents of the original from it store a new release callback.

It's super not valid to give back a result without the release callback.

[Saman Sami, 2017/02/06 23:09:54]

I can't set the release callback here. Remember that it will be lost over mojo,
so there is no point. The client of MojoCompositorFrameSinkPrivate is required
to set the release callback appropriately.

[danakj, 2017/02/06 23:24:08]

There should be a release callback made when it comes out of mojo too.

[danakj, 2017/02/06 23:24:44]

And if you don't do this here, how does the texture ever get returned in the
current patch? Clients will try to use that callback.

+}
+
 }  // namespace cc