LibWeb: Align NavigationParams and the creation AOs to the spec

And remove assorted spec FIXMEs along the way. Also align
populate_session_history_entry_document to the spec, with a bonus spec
bug to be filed.

This involves creating a new NonFetchSchemeNavigationParams spec, and
having the associated AOs take a Variant rather than Optional to
accomodate the fact that this extra struct could be returned by the
algorithm. We don't actually *do* anything with these params, but the
scaffolding is there now, with less TODOs.

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -236,7 +236,13 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Document>> Document::create_and_initialize(
         HTML::WindowEnvironmentSettingsObject::setup(
             creation_url.value(),
             move(realm_execution_context),
-            navigation_params.reserved_environment,
+            navigation_params.reserved_environment.visit(
+                // FIXME: Environment is virtual. We *really* shouldn't be slicing it here
+                [](Empty const&) -> Optional<HTML::Environment> { return {}; },
+                [](HTML::Environment* env) -> Optional<HTML::Environment> { if (env) return *env; return {}; },
+                [](JS::NonnullGCPtr<HTML::EnvironmentSettingsObject>) -> Optional<HTML::Environment> {
+                    TODO();
+                }),
             top_level_creation_url.value(),
             top_level_origin);
     }

Userland/Libraries/LibWeb/DOM/Document.h

@@ -445,6 +445,10 @@ public:
     bool is_initial_about_blank() const { return m_is_initial_about_blank; }
     void set_is_initial_about_blank(bool b) { m_is_initial_about_blank = b; }
 
+    // https://html.spec.whatwg.org/multipage/dom.html#concept-document-about-base-url
+    Optional<AK::URL> about_base_url() const { return m_about_base_url; }
+    void set_about_base_url(Optional<AK::URL> url) { m_about_base_url = url; }
+
     DeprecatedString domain() const;
     void set_domain(String const&);
 
@@ -655,6 +659,9 @@ private:
     // https://html.spec.whatwg.org/multipage/dom.html#is-initial-about:blank
     bool m_is_initial_about_blank { false };
 
+    // https://html.spec.whatwg.org/multipage/dom.html#concept-document-about-base-url
+    Optional<AK::URL> m_about_base_url;
+
     // https://html.spec.whatwg.org/multipage/dom.html#concept-document-coop
     HTML::CrossOriginOpenerPolicy m_cross_origin_opener_policy;
 

Userland/Libraries/LibWeb/DOM/DocumentLoading.cpp

@@ -263,7 +263,7 @@ JS::GCPtr<DOM::Document> load_document(Optional<HTML::NavigationParams> navigati
     auto& realm = document->realm();
 
     if (navigation_params->response->body()) {
-        auto process_body = [navigation_params, document](ByteBuffer bytes) {
+        auto process_body = [document](ByteBuffer bytes) {
             if (!parse_document(*document, bytes)) {
                 dbgln("FIXME: Load html page with an error if parsing failed.");
             }
@@ -307,32 +307,35 @@ JS::GCPtr<DOM::Document> create_document_for_inline_content(JS::GCPtr<HTML::Navi
 
     // 4. Let navigationParams be a new navigation params with
     //    id: navigationId
+    //    navigable: navigable
     //    request: null
     //    response: a new response
     //    origin: origin
+    //    fetch controller: null
+    //    commit early hints: null
+    //    COOP enforcement result: coopEnforcementResult
+    //    reserved environment: null
     //    policy container: a new policy container
     //    final sandboxing flag set: an empty set
     //    cross-origin opener policy: coop
-    //    COOP enforcement result: coopEnforcementResult
-    //    reserved environment: null
-    //    navigable: navigable
     //    FIXME: navigation timing type: navTimingType
-    //    FIXME: fetch controller: fetch controller
-    //    FIXME: commit early hints: null
+    //    about base URL: null
     auto response = Fetch::Infrastructure::Response::create(vm);
     response->url_list().append(AK::URL("about:error")); // AD-HOC: https://github.com/whatwg/html/issues/9122
     HTML::NavigationParams navigation_params {
         .id = navigation_id,
+        .navigable = navigable,
         .request = {},
         .response = *response,
+        .fetch_controller = nullptr,
+        .commit_early_hints = nullptr,
+        .coop_enforcement_result = move(coop_enforcement_result),
+        .reserved_environment = {},
         .origin = move(origin),
         .policy_container = HTML::PolicyContainer {},
         .final_sandboxing_flag_set = HTML::SandboxingFlagSet {},
         .cross_origin_opener_policy = move(coop),
-        .coop_enforcement_result = move(coop_enforcement_result),
-        .reserved_environment = {},
-        .browsing_context = navigable->active_browsing_context(),
-        .navigable = navigable,
+        .about_base_url = {},
     };
 
     // 5. Let document be the result of creating and initializing a Document object given "html", "text/html", and navigationParams.