Recent changes to v8-to-istanbul cause issues for Node 10

[bcoe]

Recent changes (https://github.com/istanbuljs/v8-to-istanbul/pull/173) are causing issues for Node 10 tests.

Specifically, it's causing branches to no longer be marked as covered in the following code:

#!/usr/bin/env node
'use strict'

if (true) {
  console.info('hello world')
} else {
  console.info('goodnight moon')
}

I would prefer not to rollback since 173 is a great change to the library, but we should dig into this (as it might be breaking Node 10 users).

CC: @glromeo