The HTML spec tells has some special rules for <body> and <frameset>
elements' onfoo event handler attributes. In some cases, the implicitly
generated event listeners should end up on the relevant global object
instead of the element itself.
This patch implements the first part of that behavior.
This logic was kept in the GlobalEventHandlers mixing for sharing
between Document and HTMLElement, but there are other interfaces who
need to support `onfoo` attribute event listeners as well.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
The internal C++ function will now receive a RefPtr<EventListener> for
'EventListener?' and a NonnullRefPtr<EventListener> for 'EventListener'.
Examples of this are addEventListener() and removeEventListener(), which
both have nullable callback parameters.
