[ie/youtube] Detect experiment binding GVS PO Token to video id (#14471)

Fixes https://github.com/yt-dlp/yt-dlp/issues/14421

Authored by: coletdjnz

yt_dlp/extractor/youtube/pot/provider.py

@@ -58,6 +58,8 @@ class PoTokenRequest:
     visitor_data: str | None = None
     data_sync_id: str | None = None
     video_id: str | None = None
+    # Internal, YouTube experiment on whether to bind GVS PO Token to video_id.
+    _gvs_bind_to_video_id: bool = False
 
     # Networking parameters
     request_cookiejar: YoutubeDLCookieJar = dataclasses.field(default_factory=YoutubeDLCookieJar)

yt_dlp/extractor/youtube/pot/utils.py

@@ -42,6 +42,9 @@ def get_webpo_content_binding(
     if not client_name or client_name not in webpo_clients:
         return None, None
 
+    if request.context == PoTokenContext.GVS and request._gvs_bind_to_video_id:
+        return request.video_id, ContentBindingType.VIDEO_ID
+
     if request.context == PoTokenContext.GVS or client_name in ('WEB_REMIX', ):
         if request.is_authenticated:
             return request.data_sync_id, ContentBindingType.DATASYNC_ID