When some CSS construct holds a name of some kind, and a CSSOM API makes it possible to read that name back to JS, should we return a serialized ident, or the actual internal value?

Using the name a\9 b (U+0009 => TAB) I checked a number of at-rules that expose their name in some way, and the result varies from rule to rule and from browser to browser. It doesn't appear to be consistently specified in one way either.

Chrome:

@layer (statement): a\9 b
@layer (block): a\9 b
@container: a\9 b
@property: --a	b
@position-try: --a	b
@keyframes: a	b
@font-palette-values: --a	b
@font-feature-values: "a\9 b"

Firefox:

@layer (statement): a\9 b
@layer (block): a\9 b
@container: a\9 b
@property: --a	b
@position-try: (N/A)
@keyframes: a	b
@font-palette-values: --a\9 b
@font-feature-values: a\9 b

Safari:

@layer (statement): a\9 b
@layer (block): a\9 b
@container: a\9 b
@property: --a	b
@position-try: (N/A)
@keyframes: a	b
@font-palette-values: --a	b
@font-feature-values: a	b

We should establish a guideline here, so that we don't continue to just arbitrarily pick something when adding new rules. I'm not sure what's best.

cc @emilio , @cdoublev

EDIT: Typo.