Bug 1534880 [wpt PR 15493] - Update algorithm to find ChromeDriver to…

… download, a=testonly

Automatic update from web-platform-tests
Update algorithm to find ChromeDriver to download (#15493)

* Update algorithm of find ChromeDriver to download

Find ChromeDriver to download, based on recommendation from
https://sites.google.com/a/chromium.org/chromedriver/downloads/version-selection

* Fall back to tip-of-tree Chromium build

Also support "Chromium" (in addition to "Google Chrome") when parsing
version strings.

* Various misc style improvements

* Factor URL construction out
* Fix logging (mozlog does not support lazy format strings)
* Fix whitespaces (two blank lines between classes, one space after #)

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wpt-commits: 681d9f6ee13ac20d3cf72928cf97d84bca56e29a
wpt-pr: 15493

UltraBlame original commit: 8b321ae6184ac62375637d8d06084bdd30cc6f92