Mus+Ash: propagate Surface ID to parents

services/ui/public/cpp/surface_id_handler.h

Index: services/ui/public/cpp/surface_id_handler.h
diff --git a/services/ui/public/cpp/surface_id_handler.h b/services/ui/public/cpp/surface_id_handler.h
new file mode 100644
index 0000000000000000000000000000000000000000..77bacfd1396d05edbd5bba59b577e0ebb1ef6e0f
--- /dev/null
+++ b/services/ui/public/cpp/surface_id_handler.h
@@ -0,0 +1,44 @@
+// 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;
+
+// Holds information about the current surface held by a Window.
+// |surface_id| uniquely identifies the surface in the display
+// compositor.
+// |surface_sequence| is a reference to the surface to retain
+// this surface even after a new surface has been created.
+// |frame_size| is the size of the frame held by the surface.
+// |device_scale_factor| is the scale factor that the frame was
+// renderered for.
+struct SurfaceInfo {
+  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_