Mus+Ash: propagate Surface ID to parents

services/ui/public/cpp/surface_id_handler.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_PUBLIC_CPP_SURFACE_ID_HANDLER_H_
+#define SERVICES_UI_PUBLIC_CPP_SURFACE_ID_HANDLER_H_
+
+#include "cc/surfaces/surface_id.h"
+#include "cc/surfaces/surface_sequence.h"
+#include "ui/gfx/geometry/size.h"
+
+namespace ui {
+
+class Window;
+
+struct SurfaceInfo {

[sky, 2016/10/14 22:44:36]

Please add a description.

[Fady Samuel, 2016/10/14 23:09:50]

Done.

+  cc::SurfaceId surface_id;
+  cc::SurfaceSequence surface_sequence;
+  gfx::Size frame_size;
+  float device_scale_factor;
+};
+
+class SurfaceIdHandler {
+ public:
+  // Called when a child window allocates a new surface ID.
+  // If the handler wishes to retain ownership of the |surface_info|,
+  // it can move it. If a child's surface has been cleared then
+  // |surface_info| will refer to a null pointer.
+  virtual void OnChildWindowSurfaceChanged(
+      Window* window,
+      std::unique_ptr<SurfaceInfo>* surface_info) = 0;
+};
+
+}  // namespace ui
+
+#endif  // SERVICES_UI_PUBLIC_CPP_SURFACE_ID_HANDLER_H_