Implements:
https://html.spec.whatwg.org/multipage/browsing-the-web.html#attempt-to-populate-the-history-entry's-document
This is going to be a replacement for `FrameLoader::load()` after
switching to navigables.
Brief description of `populate_session_history_entry_document`:
- If navigation params have url with fetch scheme then DOM document
will be populated by fetching url and parsing response. This
is going to be a replacement for `FrameLoader::load(AK::URL&)`.
- If url in navigation params is abort:srcdoc then DOM document
will be populated by parsing HTML text passed in document resource.
This is going to be a replacement for `FrameLoader::load_html()`
This will be used to look up a document's node navigable. It might be
nice to have a direct pointer from Document to its Navigable, but at
the moment I don't understand the algorithms well enough to maintain
that linkage.
This is the first step towards implementing the new "navigable" concept
from the HTML spec.
Co-authored-by: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
