SpectorJS is a third-party library that can be used to inspect any WebGL content. As for Luna, Spector can be a helpful tool when it comes to frame-by-frame debugging.
Spector Instructional Videos
Here are some instructional videos explaining how SpectorJS can be used.
For more information about how SpectorJS works check out their documentation.
When running a develop build or a specific ad network build, you can add the
?spector=1 argument at the end of the URL in order to use the frame debugger.
Then press the red record button at the top and wait a moment. A panel with information about what is being drawn in a single frame will appear.