Add appendHTML, prependHTML, beforeHTML, afterHTML, and replaceWithHTML, alongside their *Unsafe variants.

Use 3 helper algorithms for HTML insertion (pre-insert/replace/set), and call those from the appropriate web-exposed method.

ChildNode methods fail silently when the child has no parent, like their equivalent DOM methods,
and fails with a HierarchyRequestError for an invalid parent.

Closes #10122

• At least two implementers are interested (and none opposed):
  • Chrome
  • ?
• Tests are written and can be reviewed and commented upon at:
  • …
• Implementation bugs are filed:
  • Chromium: Implemented
• Corresponding HTML AAM & ARIA in HTML issues & PRs: N/A
• MDN issue is filed: Will be done as part of Blink shipping
• The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

/dynamic-markup-insertion.html ( diff )