Once ESMification (bug 1308512) finishes, we'll be able to remove one of the biggest consumer of non-syntactic scope.
We should revisit the remaining consumer and think about the requirement and possible optimization with possibly slight change on the semantics.

One possible optimization is explained in bug 793345, that we can change the global variable declaration semantics, to allow shadowing the environment properties.
That way frontend can collect the known bindings and we can emit more optimized code for access for known global variables.

\o/ \o/