Mustash: Ensure surfaces submitted to Mus by WM and embedders contain Surfaces with embeded content.

ui/aura/mus/client_surface_embedder.h

+// Copyright 2017 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.
+
+#include <memory>
+
+#include "base/macros.h"
+
+namespace ui {
+class Layer;
+}
+
+namespace aura {
+
+struct SurfaceInfo;
+class Window;
+
+// Used by WindowPortMus when it is embedding a client. Responsible for setting
+// up layers containing content from the client, parenting them to the window's
+// layer, and updating them when the client submits new surfaces.
+class ClientSurfaceEmbedder {
+ public:
+  explicit ClientSurfaceEmbedder(Window* window);
+  ~ClientSurfaceEmbedder();
+
+  // Updates the surface layer and the clip layer based on the surface info.
+  void UpdateSurface(const SurfaceInfo& surface_info);
+
+ private:
+  // The window which embeds the client.
+  Window* window_;
+
+  // Contains the client's content.
+  std::unique_ptr<ui::Layer> surface_layer_;
+
+  // Used for clipping the surface layer to the window bounds.
+  std::unique_ptr<ui::Layer> clip_layer_;
+
+  DISALLOW_COPY_AND_ASSIGN(ClientSurfaceEmbedder);
+};
+
+}  // namespace aura