CSSStyleDeclaration was added to the _preHideInternals non-enumerable
pre-declaration list (commit c7e7c70) on the assumption that its later
`globalThis.X = X` assignment would fill in the value. But it was the only
one of the 22 WebIDL interfaces with no such assignment, so its value stayed
undefined: `typeof window.CSSStyleDeclaration` was "undefined" while
`'CSSStyleDeclaration' in window` was true, and because it is the type of
element.style / getComputedStyle(), `el.style instanceof CSSStyleDeclaration`
threw "Right-hand side of 'instanceof' is not callable" (Chrome returns true).
Assign globalThis.CSSStyleDeclaration alongside the other interface globals.
The property was already declared writable/configurable, so the assignment
only updates the value and it remains enumerable:false, like a real browser.
Fixes#546
Andrey Mnatsakanov
a0e1ba5f85