Frédéric Wang

cc @koto @lukewarlow Note that this PR applies on top of https://github.com/w3c/trusted-types/pull/555 ; only the [second commit](https://github.com/w3c/trusted-types/pull/556/commits/c6007f0f12d9b1feb5c65e6d4c84e25f573f9ea1) is relevant here.

So IIUC, the problem is the confusion with [Element.tagName](https://dom.spec.whatwg.org/#dom-element-tagname)) which returns uppercased qualified name. So the suggestion is to rename the `tagName` parameter to use `localName` instead?

cc @smaug---- So another source of confusion is the "attribute" argument from `getAttributeType()`. Comparing with [createAttribute(https://dom.spec.whatwg.org/#dom-document-createattribute)] and [createAttributeNS](https://dom.spec.whatwg.org/#dom-document-createattributens), it could better be renamed "local name" or "qualified name". Besides lowercasing...

cc @pepelsbey See also https://github.com/mdn/browser-compat-data/issues/24681

I'm going to implement getPropertyType/getAttributeType in Firefox, so I'll make sure we have enough test coverage.

Uploaded something there: https://phabricator.services.mozilla.com/D226122

I think this can be closed since that's addressed by https://github.com/web-platform-tests/wpt/commit/3f6b218762b8df9b6d14e19d3f115b0722c3289f and https://github.com/web-platform-tests/wpt/commit/da5e743e23b8ab8f72a228d45b074d75edf5cd3f#diff-bbed4f84dea0d96f255fd583d63ad05036783ba823398da9fa38d6496f31432eR118 https://github.com/web-platform-tests/wpt/pull/48769 will also check explicit null values.

cc @lukewarlow @koto

Same for the properties: https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/trustedtypes/trusted_type_policy_factory.cc;drc=08efa89c7d73d72e6ebcddbf053c41a230dc1ba8;l=92?q=TrustedTypePolicyFactory

> They were historically included but no longer are. Chromium needs to update it's implementation such that they're no longer protected. It might be worth adding a test that ensured...