Per spec, document objects have a throw-on-dynamic-markup-insertion counter, which is used in conjunction with the create an element for the token algorithm to prevent custom element constructors from being able to use document.open(), document.close(), and document.write() when they are invoked by the parser.
Tag UXP Issue #1344
CheckForOutdatedParent()
This was only used to check for cases when document.open() changed the
global, and elements being inserted into the document needing a new
reflector as a result.
Since document.open() no longer changes the global, this code is no
longer needed.
This changes the work we do for document.open() in the following ways:
- We no longer create a new Window when doing document.open().
We use the same Window but remove all the event listeners on the
existing DOM tree and Window before removing the document's existing
children to provide a clean slate document to use for .write().
- We no longer create a session history entry (previously would be a
wyciwyg URI). We now replace the current one, effectively losing the
entry for the original document.
- We now support document.open() on windowless documents.
