style(*): IE is a real browser, and chakra is pretty solid

- IE9+ do not have issues with Function.prototype.apply() on builtin fns (asked Brian Terlson)
  (NOTE: there may still be corner cases where builtins will not have `apply()` --- this may
  need to be reverted on complaint).
- HTMLScriptElement#text is an IDL-spec'd attribute, and we use it in all cases --- so the
  comment was sort of nonsense.
- The value of `msie` does not depend on whether the user is using a "real" browser or not.

Closes #10242