LibWeb: Add about base url to the various AOs that construct documents

And some assorted cleanup along the way. The browsing context and
document AOs in particular need re-alignment with the spec.

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -269,6 +269,7 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> Document::create_and_initialize(
     document->set_url(*creation_url);
     document->m_navigation_id = navigation_params.id;
     document->m_readiness = HTML::DocumentReadyState::Loading;
+    document->m_about_base_url = navigation_params.about_base_url;
 
     document->m_window = window;
 

Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp

@@ -121,11 +121,17 @@ WebIDL::ExceptionOr<BrowsingContext::BrowsingContextAndDocument> BrowsingContext
     // 3. Let creatorOrigin be null.
     Optional<Origin> creator_origin = {};
 
+    // FIXME: This algorithm needs re-aligned with the spec
+    Optional<AK::URL> creator_base_url = {};
+
     // 4. If creator is non-null, then:
     if (creator) {
         // 1. Set creatorOrigin to creator's origin.
         creator_origin = creator->origin();
 
+        // FIXME: This algorithm needs re-aligned with the spec
+        creator_base_url = creator->base_url();
+
         // FIXME: 2. Set browsingContext's creator base URL to an algorithm which returns creator's base URL.
 
         // FIXME: 3. Set browsingContext's virtual browsing context group ID to creator's browsing context's top-level browsing context's virtual browsing context group ID.
@@ -211,6 +217,9 @@ WebIDL::ExceptionOr<BrowsingContext::BrowsingContextAndDocument> BrowsingContext
     // is initial about:blank: true
     document->set_is_initial_about_blank(true);
 
+    // about base URL: creatorBaseURL
+    document->set_about_base_url(creator_base_url);
+
     // 15. If creator is non-null, then:
     if (creator) {
         // 1. Set document's referrer to the serialization of creator's URL.

Userland/Libraries/LibWeb/HTML/Navigable.cpp

@@ -1531,6 +1531,7 @@ WebIDL::ExceptionOr<void> Navigable::navigate_to_a_javascript_url(AK::URL const&
     document_state->set_request_referrer_policy(old_doc_state->request_referrer_policy());
     document_state->set_initiator_origin(initiator_origin);
     document_state->set_origin(initiator_origin);
+    document_state->set_about_base_url(old_doc_state->about_base_url());
     document_state->set_ever_populated(true);
     document_state->set_navigable_target_name(old_doc_state->navigable_target_name());
 

Userland/Libraries/LibWeb/HTML/NavigableContainer.cpp

@@ -80,12 +80,18 @@ WebIDL::ExceptionOr<void> NavigableContainer::create_new_child_navigable()
         target_name = String::from_deprecated_string(value).release_value_but_fixme_should_propagate_errors();
 
     // 6. Let documentState be a new document state, with
-    //    document: document
+    //  - document: document
-    //    navigable target name: targetName
+    //  - initiator origin: document's origin
+    //  - origin: document's origin
+    //  - navigable target name: targetName
+    //  - about base URL: document's about base URL
     JS::NonnullGCPtr<DocumentState> document_state = *heap().allocate_without_realm<HTML::DocumentState>();
     document_state->set_document(document);
+    document_state->set_initiator_origin(document->origin());
+    document_state->set_origin(document->origin());
     if (target_name.has_value())
         document_state->set_navigable_target_name(*target_name);
+    document_state->set_about_base_url(document->about_base_url());
 
     // 7. Let navigable be a new navigable.
     JS::NonnullGCPtr<Navigable> navigable = *heap().allocate_without_realm<Navigable>();

Userland/Libraries/LibWeb/HTML/TraversableNavigable.cpp

@@ -71,9 +71,18 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<TraversableNavigable>> TraversableNavigable
     // document: document
     document_state->set_document(document);
 
+    // initiator origin: null if opener is null; otherwise, document's origin
+    document_state->set_initiator_origin(opener ? Optional<Origin> {} : document->origin());
+
+    // origin: document's origin
+    document_state->set_origin(document->origin());
+
     // navigable target name: targetName
     document_state->set_navigable_target_name(target_name);
 
+    // about base URL: document's about base URL
+    document_state->set_about_base_url(document->about_base_url());
+
     // 5. Let traversable be a new traversable navigable.
     auto traversable = vm.heap().allocate_without_realm<TraversableNavigable>(page);