Node.js v6 was end-of-life'd in April, 2019, with AWS Lambda prohibiting updaets to the Node.js v6 runtime since June 30, 2019.
This makes it quite safe for us to remove the Node 6 support from the repository.
These getters are introduced as a more convenient substitute for
a `require('puppeteer/Errors')` and
`require('puppeteer/DeviceDescriptors')`.
This way we can make cross-browser story nicer - a single require
of `puppeteer` or `puppeteer-firefox` fully defines Puppeteer
environment.