This reverts commit f09ab88891, reversing
changes made to effc761e0e.
This is being temporarily reverted to make it easier to release an
urgent fix for v10.15.1.
* deprecate extensionizer for webextension-polyfill
* fix tests
* remove extensionizer
* fix browser windows api calls
* fix broken on firefox
* fix getAcceptLanguages call
* update more browser apis that are now promisified
* remove unnecessary console error ignoring in e2e tests