Description

This PR fixes a memory leak issue in the TrackButton component.
Currently, TrackButton attaches event listeners to TextTrackList and the player instance, but only removes some of them when the player is disposed. If a TrackButton instance itself is disposed (e.g. when custom text tracks are removed/added dynamically), the listeners remain active, causing stale references and potential leaks.

The issue was noticed when dynamically removing and adding text tracks in CaptionsButton or TrackButton components — old listeners were not cleaned up, leading to unexpected behavior, memory usage growth and errors like main.js:1685 VIDEOJS: ERROR: Error: Invalid target for null#on; must be a DOM node or evented object..

Specific Changes proposed

• Store references to updateHandler and disposeHandler as private properties (this.updateHandler_, this.disposeHandler_).
• Override dispose() to:
  • Remove all attached listeners from TextTrackList and the player.
  • Clear the handler references (delete this.updateHandler_, delete this.disposeHandler_).
  • Call super.dispose() afterwards.

Requirements Checklist

• Feature implemented / Bug fixed
• Tests are passing (manual verification, no regressions observed)
• Documentation updated (inline JSDoc for dispose())

Note: Currently using delete this.updateHandler_ for cleanup. If maintainers prefer = null for consistency/performance, I can update accordingly.