[Gstreamer][Westeros] Bring back westeros autoplug code for playbin3

https://bugs.webkit.org/show_bug.cgi?id=263714

Reviewed by Philippe Normand.

To autoplug westeros sink in playbin3 we need to specify the stop caps to ensure encoded data goes directly into the
sink.

This is a revert of # https://commits.webkit.org/266178@main.

* Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:
(WebCore::MediaPlayerPrivateGStreamer::syncOnClock):
(WebCore::MediaPlayerPrivateGStreamer::configureElementPlatformQuirks):

Canonical link: https://commits.webkit.org/269808@main

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

@@ -984,8 +984,6 @@ void MediaPlayerPrivateGStreamer::syncOnClock(bool sync)
 #if !USE(WESTEROS_SINK)
     setSyncOnClock(videoSink(), sync);
     setSyncOnClock(audioSink(), sync);
-#else
-    UNUSED_PARAM(sync);
 #endif
 }
 
@@ -2306,12 +2304,40 @@ void MediaPlayerPrivateGStreamer::configureElementPlatformQuirks(GstElement* ele
 #endif
 #endif
 
+#if USE(WESTEROS_SINK)
+    static GstCaps* westerosSinkCaps = nullptr;
+    static GType westerosSinkType = G_TYPE_INVALID;
+    static std::once_flag onceFlag;
+    std::call_once(onceFlag, [] {
+        GRefPtr<GstElementFactory> westerosfactory = adoptGRef(gst_element_factory_find("westerossink"));
+        if (westerosfactory) {
+            gst_object_unref(gst_plugin_feature_load(GST_PLUGIN_FEATURE(westerosfactory.get())));
+            westerosSinkType = gst_element_factory_get_element_type(westerosfactory.get());
+            for (auto* t = gst_element_factory_get_static_pad_templates(westerosfactory.get()); t; t = g_list_next(t)) {
+                GstStaticPadTemplate* padtemplate = static_cast<GstStaticPadTemplate*>(t->data);
+                if (padtemplate->direction != GST_PAD_SINK)
+                    continue;
+                if (westerosSinkCaps)
+                    westerosSinkCaps = gst_caps_merge(westerosSinkCaps, gst_static_caps_get(&padtemplate->static_caps));
+                else
+                    westerosSinkCaps = gst_static_caps_get(&padtemplate->static_caps);
+            }
+        }
+    });
 #if ENABLE(MEDIA_STREAM)
     if (m_streamPrivate && !g_strcmp0(G_OBJECT_TYPE_NAME(G_OBJECT(element)), "GstWesterosSink") && gstObjectHasProperty(element, "immediate-output")) {
         GST_DEBUG_OBJECT(pipeline(), "Enable 'immediate-output' in WesterosSink");
         g_object_set(element, "immediate-output", TRUE, nullptr);
     }
 #endif
+    if (!m_isLegacyPlaybin && westerosSinkCaps && g_str_has_prefix(GST_ELEMENT_NAME(element), "uridecodebin3")) {
+        GRefPtr<GstCaps> defaultCaps;
+        g_object_get(element, "caps", &defaultCaps.outPtr(), NULL);
+        defaultCaps = adoptGRef(gst_caps_merge(gst_caps_ref(westerosSinkCaps), defaultCaps.leakRef()));
+        g_object_set(element, "caps", defaultCaps.get(), NULL);
+        GST_INFO_OBJECT(pipeline(), "setting stop caps tp %" GST_PTR_FORMAT, defaultCaps.get());
+    }
+#endif
 
 #if ENABLE(MEDIA_STREAM) && PLATFORM(REALTEK)
     if (m_streamPrivate) {