[GStreamer] Fix readyState calculations

https://bugs.webkit.org/show_bug.cgi?id=248217

Reviewed by Philippe Normand.

On some platforms, the audio sink is acting as a fake sink while the decoder fetches data
from the pipeline and transfers it to the SoC drivers, even in READY and PAUSED states,
meaning we cannot rely on buffering messages anymore.

However, on that platform the audio sinks implements buffering queries, that are currently
issued to the entire pipeline, which on some platforms may yield misleading results
if some random element implements buffering queries and receives that query first.

Thus this patch first queries the audio sink, before trying the video sink and finally
the pipeline itself.

Original author: Pawel Lampe <pawel.lampe@gmail.com>
See: WebPlatformForEmbedded/WPEWebKit#975

* Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:
(WebCore::MediaPlayerPrivateGStreamer::updateStates): Send buffering query to audio/video sinks first

Canonical link: https://commits.webkit.org/257066@main

Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp

@@ -2337,9 +2337,12 @@ void MediaPlayerPrivateGStreamer::updateStates()
                 GRefPtr<GstQuery> query = adoptGRef(gst_query_new_buffering(GST_FORMAT_PERCENT));
 
                 m_isBuffering = m_bufferingPercentage < 100;
-                if (gst_element_query(m_pipeline.get(), query.get())) {
+                if ((m_audioSink && gst_element_query(m_audioSink.get(), query.get()))
+                    || (m_videoSink && gst_element_query(m_videoSink.get(), query.get()))
+                    || gst_element_query(m_pipeline.get(), query.get())) {
                     gboolean isBuffering = m_isBuffering;
                     gst_query_parse_buffering_percent(query.get(), &isBuffering, nullptr);
+                    GST_TRACE_OBJECT(pipeline(), "[Buffering] m_isBuffering forcefully updated from %d to %d", m_isBuffering, isBuffering);
                     m_isBuffering = isBuffering;
                 }