Mus+Ash: propagate Surface ID to parents

services/ui/surfaces/display_compositor_client.h

+// Copyright 2016 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 SERVICES_UI_SURFACES_DISPLAY_COMPOSITOR_CLIENT_H_
+#define SERVICES_UI_SURFACES_DISPLAY_COMPOSITOR_CLIENT_H_
+
+namespace ui {
+
+// TODO(fsamuel: In the future, this will be a mojo interface from mus-gpu to
+// mus-ws.
+class DisplayCompositorClient {
+ public:
+  virtual void OnSurfaceCreated(const cc::SurfaceId& surface_id,
+                                const gfx::Size& frame_size,
+                                float device_scale_factor) = 0;
+
+ protected:
+  virtual ~DisplayCompositorClient() {}
+};
+
+}  // namespace ui
+
+#endif  // SERVICES_UI_SURFACES_DISPLAY_COMPOSITOR_CLIENT_H_