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_
+
+namespace ui {
+
+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.
+  virtual void OnChildWindowSurfaceCreated(

[sky, 2016/10/14 21:55:34]

This may be called with null, right? In which case created is confusing. Created
also implies a one time thing. How about OnChildWindowSurfaceChanged(). And make
it clear this may be called with null.

[Fady Samuel, 2016/10/14 22:20:13]

Done.

+      Window* window,
+      std::unique_ptr<Window::SurfaceInfo>* surface_info) = 0;

[sky, 2016/10/14 21:55:34]

You'll need to include window.h here (which seems bad). Maybe move into it's own
header, or define it here (as a toplevel class, not in inner class).

[Fady Samuel, 2016/10/14 22:20:13]

Done.

+};
+
+}  // namespace ui
+
+#endif  // SERVICES_UI_PUBLIC_CPP_SURFACE_ID_HANDLER_H_