Validate AJAX fetched ROM before using.
Group similar functions.
Make AJAX callbacks easier to follow.
Make stored ROM loading functions easier to follow.
Improve AJAX callback messages.
Move related code block away from unrelated code.
Improve comments.
Rename function and group with similar functions.
Improve drop file validation failure messages.
Make drop-file-validation callback logic easier to follow.
Rename functions for consistency.
Change order of functions.
Rework callback code so more easily understood.
Remove unhelpful messages.
Revise message.
Revise comments.
Revise and remove messages.
Rename function.
Remove unused arguments from function.
Make callback flow easier to follow.