Taskbartabs topsites

[AllegroFox]

Adds targeting to support the "Top Sites" taskbar tabs spotlight experiment.

• browser.taskbarTabs.enabled == true
• no web app currently pinned (measure net-new adoption)
• profileAge 7+ days
• Windows only (taskbar tabs is currently limited to Windows)

[jaredlockhart]

Ah @AllegroFox

FAILED experimenter/targeting/tests/test_targeting_configs.py::TestTargetingConfigs::test_validate_targeting_config_fields_305 - AssertionError: {'installedWebAppsCount'} is not false : Unknown targeting fields in existing_windows_user_taskbar_tabs_enabled_but_not_used: {'installedWebAppsCount'}

installedWebAppsCount is not instrumented as a Nimbus targeting field:

See docs here https://experimenter.info/platform-guides/desktop/targeting#adding-new-targeting-options

[AllegroFox]

Ah @AllegroFox

FAILED experimenter/targeting/tests/test_targeting_configs.py::TestTargetingConfigs::test_validate_targeting_config_fields_305 - AssertionError: {'installedWebAppsCount'} is not false : Unknown targeting fields in existing_windows_user_taskbar_tabs_enabled_but_not_used: {'installedWebAppsCount'}

installedWebAppsCount is not instrumented as a Nimbus targeting field:

See docs here https://experimenter.info/platform-guides/desktop/targeting#adding-new-targeting-options

Ah shoot, I overlooked that! I thought I had tested it through the Nimbus Devtools and it was present. In that case, I think we'll go with keeping that part of the targeting at the message level.