This requires copying usage flags from the outer scope to the
arrow scope upon encountering the arrow token.

In order to properly pass-on the calls_eval bit, now record
that bit on script scopes just like everywhere else, and add
necessary code to scopes.cc to handle that change in behavior.

Also factored out scope flag propagation to its own method to
make the call site simple (though note that only the eval
bit makes any difference for arrows).

BUG=v8:4395
LOG=n

Review URL: https://codereview.chromium.org/1423613002

Cr-Commit-Position: refs/heads/master@{#31660}