Revert " Use Cell/RefCell for interior mutability of Frame."

This reverts commit 70f118e00971a0eae551fca30f8d1c564ec791e5.
fixup! Use Cell/RefCell for interior mutability of XMLHttpRequest.
fixup! Use Cell/RefCell for interior mutability of NodeList, Performance, TestBinding, and ValidityState.
fixup! JS<T> contains '*T' instead of RefCell.
fixup! Use Cell/RefCell for interior mutability of Attr, AttrList, Blob, BrowserContext, ClientRect, and ClientRectList.