[geometry] new DOMMatrix().toString() works differently when executed in a web worker

[SimonSiefke]

Spec Link

https://drafts.fxtf.org/geometry/#dommatrixreadonly

interface DOMMatrixReadOnly {
    [Exposed=Window] stringifier;
}

What steps will reproduce the problem?

1. In a devtools console, evaluate console.log(new DOMMatrix().toString())
2. In a devtools web worker console, evaluate console.log(new DOMMatrix().toString())

What is the expected result?

new DOMMatrix().toString() behaves the same in the main thread as in a web worker, new DOMMatrix().toString() should be matrix(1, 0, 0, 1, 0, 0).

What happens instead?

Inside the main thread: new DOMMatrix().toString() === matrix(1, 0, 0, 1, 0, 0)
Inside a web worker : new DOMMatrix().toString() === [object DOMMatrix]

Additional Information

The same issue occurs for DOMMatrixReadOnly.