exo: Implement notification surface support

components/exo/notification_surface.h

Index: components/exo/notification_surface.h
diff --git a/components/exo/notification_surface.h b/components/exo/notification_surface.h
new file mode 100644
index 0000000000000000000000000000000000000000..1c676d55c02a2d15967b770cbba56a62b10ef486
--- /dev/null
+++ b/components/exo/notification_surface.h
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+// 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 COMPONENTS_EXO_NOTIFICATION_SURFACE_H_
+#define COMPONENTS_EXO_NOTIFICATION_SURFACE_H_
+
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "components/exo/surface_delegate.h"
+#include "components/exo/surface_observer.h"
+#include "ui/gfx/geometry/size.h"
+
+namespace aura {
+class Window;
+}
+
+namespace exo {
+class NotificationSurfaceManager;
+class Surface;
+
+// Handles notification surface role of a given surface.
+class NotificationSurface : public SurfaceDelegate, public SurfaceObserver {
+ public:
+  NotificationSurface(NotificationSurfaceManager* manager,
+                      Surface* surface,
+                      const std::string& notification_id);
+  ~NotificationSurface() override;
+
+  gfx::Size GetSize() const;
+
+  aura::Window* window() { return window_.get(); }
+  const std::string& notification_id() const { return notification_id_; }
+
+ private:
+  // Overridden from SurfaceDelegate:
+  void OnSurfaceCommit() override;
+  bool IsSurfaceSynchronized() const override;
+
+  // Overridden from SurfaceObserver:
+  void OnSurfaceDestroying(Surface* surface) override;
+
+  NotificationSurfaceManager* const manager_;  // Not owned.
+  Surface* surface_;                           // Not owned.
+  const std::string notification_id_;
+
+  std::unique_ptr<aura::Window> window_;
+
+  DISALLOW_COPY_AND_ASSIGN(NotificationSurface);
+};
+
+}  // namespace exo
+
+#endif  // COMPONENTS_EXO_NOTIFICATION_SURFACE_H_