I can see this scripts directory has some html files that were forged at different times, years apart. So, I see how this could happen, but as your new PM I'm adding a ticket (I kid).
As a customer that likes to squash bugs and warnings... This warning comes up when Spinner.html is first loaded:
The character encoding of a framed document was not declared. The document may appear different if viewed without the document framing it.
And, the reason is there is no char encoding set in the head of Spinner.html. Just an oversight, I'm sure.
After I'd added a meta tag with charset="UTF-8" the warning went away. But, then I wanted to be consistent and I opened 10 other files in the scripts dir.
All 10 had a meta tag that essentially did set the charset. Some had some more props in the meta tag. Some use "utf-8" (lowercase).
Just a low-hanging-fruit type of request here, but I think it would be nice if y'all:
1. Decided on a particular shape of this tag.
2. Made sure it was included where in every file it should be in (atleast Spinner.html as it is core).