LibVideo: Add a factory to create a PlaybackManager from in-memory data

The demuxer already has such a factory, so this just exposes the same
factory in the PlaybackManager.

Userland/Libraries/LibVideo/PlaybackManager.cpp

@@ -47,7 +47,18 @@ private:
 
 DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> PlaybackManager::from_file(StringView filename, PlaybackTimerCreator playback_timer_creator)
 {
-    NonnullOwnPtr<Demuxer> demuxer = TRY(Matroska::MatroskaDemuxer::from_file(filename));
+    auto demuxer = TRY(Matroska::MatroskaDemuxer::from_file(filename));
+    return create_with_demuxer(move(demuxer), move(playback_timer_creator));
+}
+
+DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> PlaybackManager::from_data(ReadonlyBytes data, PlaybackTimerCreator playback_timer_creator)
+{
+    auto demuxer = TRY(Matroska::MatroskaDemuxer::from_data(data));
+    return create_with_demuxer(move(demuxer), move(playback_timer_creator));
+}
+
+DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> PlaybackManager::create_with_demuxer(NonnullOwnPtr<Demuxer> demuxer, PlaybackTimerCreator playback_timer_creator)
+{
     auto video_tracks = TRY(demuxer->get_tracks_for_type(TrackType::Video));
     if (video_tracks.is_empty())
         return DecoderError::with_description(DecoderErrorCategory::Invalid, "No video track is present"sv);

Userland/Libraries/LibVideo/PlaybackManager.h

@@ -102,6 +102,7 @@ public:
     using PlaybackTimerCreator = Function<ErrorOr<NonnullOwnPtr<PlaybackTimer>>(int, Function<void()>)>;
 
     static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> from_file(StringView file, PlaybackTimerCreator = nullptr);
+    static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> from_data(ReadonlyBytes data, PlaybackTimerCreator = nullptr);
 
     PlaybackManager(NonnullOwnPtr<Demuxer>& demuxer, Track video_track, NonnullOwnPtr<VideoDecoder>&& decoder, PlaybackTimerCreator);
 
@@ -135,6 +136,8 @@ private:
     class SeekingStateHandler;
     class StoppedStateHandler;
 
+    static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> create_with_demuxer(NonnullOwnPtr<Demuxer> demuxer, PlaybackTimerCreator playback_timer_creator);
+
     void start_timer(int milliseconds);
     void timer_callback();
     Optional<Time> seek_demuxer_to_most_recent_keyframe(Time timestamp, Optional<Time> earliest_available_sample = OptionalNone());