The environment settings object is effectively the context a piece of
script is running under, for example, it contains the origin,
responsible document, realm, global object and event loop for the
current context. This effectively replaces ScriptExecutionContext, but
it cannot be removed in this commit as EventTarget still depends on it.
https://html.spec.whatwg.org/multipage/webappapis.html#environment-settings-object
Note our Attribute class is what the spec refers to as just "Attr". The
main differences between the existing implementation and the spec are
just that the spec defines more fields.
Attributes can contain namespace URIs and prefixes. However, note that
these are not parsed in HTML documents unless the document content-type
is XML. So for now, these are initialized to null. Web pages are able to
set the namespace via JavaScript (setAttributeNS), so these fields may
be filled in when the corresponding APIs are implemented.
The main change to be aware of is that an attribute is a node. This has
implications on how attributes are stored in the Element class. Nodes
are non-copyable and non-movable because these constructors are deleted
by the EventTarget base class. This means attributes cannot be stored in
a Vector or HashMap as these containers assume copyability / movability.
So for now, the Vector holding attributes is changed to hold RefPtrs to
attributes instead. This might change when attribute storage is
implemented according to the spec (by way of NamedNodeMap).
This particularly implements these two points:
- "If the adjusted current node is an HTML integration point and the
token is a start tag"
- "If the adjusted current node is an HTML integration point and the
token is a character token"
This also adds spec comments to the tree constructor.
We now fire "pageshow" events at the appropriate time during document
loading (done by the parser.)
Note that there are no corresponding "pagehide" events yet.
This will be used to determine whether "pageshow" and "pagehide" events
are appropriate. We won't actually make use of it until we implement
more of history traversal and document unloading.
The only difference from what we were already doing is that setting the
same ready state twice no longer fires a "readystatechange" event.
I don't think that could happen in practice though.
We will now spin in "the end" until there are no more "things delaying
the load event". Of course, nothing actually uses this yet, and there
are a lot of things that need to.
