Depending on the decision on this spec issue to support tag name strategy for WebDriver:FindElementFromShadowRoot and WebDriver:FindElementsFromShadowRoot we either would need to wait until spec is updated and then align the implementation with the spec or wait until shadow root supports getElementsByTagName. In the second case, most likely we would need only enable wdspec tests (https://searchfox.org/mozilla-central/source/testing/web-platform/tests/webdriver/tests/find_element_from_element/find.py#104 and https://searchfox.org/mozilla-central/source/testing/web-platform/tests/webdriver/tests/find_elements_from_shadow_root/find.py#156).

This depends on a WebDriver classic spec decision: https://github.com/w3c/webdriver/issues/1724

Actually https://github.com/w3c/webdriver/issues/1610 is the issue that we want to reference here.