851870 - warn when chrome code clones a CSSStyleSheetInner

Status: NEW

(Core :: CSS Parsing and Computation, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

We should probably have a warning when chrome code clones a CSSStyleSheetInner that is otherwise shared between prototype documents, so that we don't take the resulting memory and performance regressions (e.g., bug 851862 comment 1).

Comment 1

[Nicholas Nethercote [inactive]]

Would this be a warning in the error console?

Comment 2

[Frank Yan (:fryn)]

We should make sure it does not warn when modifying an inline style sheet that was created dynamically. Though it may not usually be best practice (and we don't currently do this in-product), the CSSOM is read-write, and there are legitimate cases to use it as such.

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Probably yes, but only under certain conditions (minimally, chrome document with a XUL Prototype Document, style sheet is initially non-empty).