Reflector is used on Chrome OS to mirror content efficiently. It's used for software mirroring, unified mode and docked magnifier. The current implementation is coupled closely with both ui::Compositor and viz::OutputSurface. With OOP-D these two pieces of code run in different processes and reflector doesn't work.

If you build Chrome OS for Linux you can test out features that use reflector. For example, you can use software mirroring by running with the following command line:

$ ./chrome.exe --ash-host-window-bounds=800x800,900+0-800x800 --ash-dev-shortcuts --ash-debug-shortcuts --user-first-display-as-internal

This will launch two displays which are by default in extended mode. If you switch to mirror mode, either by hitting ctrl+shift+m or in the display settings, you'll see the first display mirrored on the second display. If you launch OOP-D by adding --enable-features=VizDisplayCompositor then mirror mode won't work.

Instead of using reflector we can use SurfaceLayer to mirror content. This will likely perform worse without some additional display compositor changes. Please modify MirrorWindowController so it no longer uses Reflector. Something like the following:

1. Don't create a ui::Reflector (eg. where CreateReflector() is called)
2. Get the current SurfaceId for the reflected display's ui::Compositor (which we access at [1] already).
3. Set mirror_window->layer() to embed that SurfaceId. Calling Layer::SetShowPrimarySurface() should handle most of that.

The exact details need to filled in here. Once working there are a few other issues to sort out.

1. Handle when the reflected display SurfaceId changes. This will happen when displays resolution changes, on rotation, etc. MirrorWindowController will need to update the SurfaceId for the ui::Layer.
2. Handle the mirroring display resizing. This likely means modifying MirrorWindowController::OnHostResized().
3. Making sure the change also works with unified mode.

After everything above works then maybe land the change behind a flag.

[1] https://cs.chromium.org/chromium/src/ash/display/mirror_window_controller.cc?l=233&rcl=66bb07a77fc8687d203e47223a64115ae5d727aa