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.
This patch:
- introduces new testRunner methods `addTestDSL` and `addSuiteDSL`
to add annotated test / suite.
- introduces new test/suite declaration methods: `it_fails_ffox` and
`describe_fails_ffox`. These are equal to `it`/`describe` for chromium
tests and to `xit`/`xdescribe` for firefox.
- marks all unsupported tests with `it_fails_ffox`
- adds a new command-line flag `'--firefox-status'` to `//test/test.js`.
This flag dumps current amount of tests that are intentionally skipped
for Firefox.
End goal: get rid of all `it_fails_ffox` and `describe_fails_ffox`
tests.
Drive-By: remove cookie tests "afterEach" hook that was removing
cookies - it's not needed any more since every test is run in a
designated browser context.
References #3889
