Add video player (#2)

https://github.com/sony/flutter-embedded-linux/issues/124

packages/video_player/elinux/video_player_stream_handler.h

@@ -0,0 +1,32 @@
+// Copyright 2021 Sony Group Corporation. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PACKAGES_VIDEO_PLAYER_VIDEO_PLAYER_ELINUX_VIDEO_PLAYER_STREAM_HANDLER_H_
+#define PACKAGES_VIDEO_PLAYER_VIDEO_PLAYER_ELINUX_VIDEO_PLAYER_STREAM_HANDLER_H_
+
+class VideoPlayerStreamHandler {
+ public:
+  VideoPlayerStreamHandler() = default;
+  virtual ~VideoPlayerStreamHandler() = default;
+
+  // Prevent copying.
+  VideoPlayerStreamHandler(VideoPlayerStreamHandler const&) = delete;
+  VideoPlayerStreamHandler& operator=(VideoPlayerStreamHandler const&) = delete;
+
+  // Notifies the completion of initializing the video player.
+  void OnNotifyInitialized() { OnNotifyInitializedInternal(); }
+
+  // Notifies the completion of decoding a video frame.
+  void OnNotifyFrameDecoded() { OnNotifyFrameDecodedInternal(); }
+
+  // Notifies the completion of playing a video.
+  void OnNotifyCompleted() { OnNotifyCompletedInternal(); }
+
+ protected:
+  virtual void OnNotifyInitializedInternal() = 0;
+  virtual void OnNotifyFrameDecodedInternal() = 0;
+  virtual void OnNotifyCompletedInternal() = 0;
+};
+
+#endif  // PACKAGES_VIDEO_PLAYER_VIDEO_PLAYER_ELINUX_VIDEO_PLAYER_STREAM_HANDLER_H_