Consider adding --test-type chrome flag

[paulirish]

--test-type=foo has some interesting effects: https://cs.chromium.org/search/?q=kTestType%5Cb&type=cs

Need to collect its effects and make sure ALL users of chrome-launcher want these changes made.

[paulirish]

joel and i looked at it and --test-type is basically the 2014 version of --enable-automation

• It avoids creating application stubs in ~/Applications on mac.
• It makes exit codes slightly more correct
• windows navigation jumplists arent updated https://bugs.chromium.org/p/chromium/issues/detail?id=389375
• doesn't start some chrome StartPageService
• disables initializing chromecast service
• "Component extensions with background pages are not enabled during tests because they generate a lot of background behavior that can interfere."
• when quitting the browser, it disables additional checks that may stop that quitting process. (like unsaved form modifications or unhandled profile notifications..)

[paulirish]

Added these notes as docs in https://github.com/GoogleChrome/chrome-launcher/blob/master/docs/chrome-flags-for-tools.md