LibWeb/HTML: Add environment discarding steps

Exactly one place seems to define these at the moment: service worker
clients. Since we don't have a type for these and just use
EnvironmentSettingsObject, I've put it there.

Libraries/LibWeb/HTML/Navigable.cpp

@@ -1287,7 +1287,13 @@ WebIDL::ExceptionOr<void> Navigable::populate_session_history_entry_document(
 
             // 4. If navigationParams is not null, then:
             if (!navigation_params.has<NullOrError>()) {
-                // FIXME: 1. Run the environment discarding steps for navigationParams's reserved environment.
+                // 1. Run the environment discarding steps for navigationParams's reserved environment.
+                navigation_params.visit(
+                    [](GC::Ref<NavigationParams> const& it) {
+                        it->reserved_environment->discard_environment();
+                    },
+                    [](auto const&) {});
+
                 // FIXME: 2. Invoke WebDriver BiDi navigation failed with navigable and a new WebDriver BiDi navigation status whose id is navigationId, status is "canceled", and url is navigationParams's response's URL.
             }
         }

Libraries/LibWeb/HTML/Scripting/Environments.cpp

@@ -67,6 +67,15 @@ void EnvironmentSettingsObject::visit_edges(Cell::Visitor& visitor)
     visitor.visit(m_service_worker_object_map);
 }
 
+void EnvironmentSettingsObject::discard_environment()
+{
+    // https://w3c.github.io/ServiceWorker/#ref-for-environment-discarding-steps
+    // Each service worker client has the following environment discarding steps:
+
+    // 1. Set client’s discarded flag.
+    set_discarded(true);
+}
+
 JS::ExecutionContext& EnvironmentSettingsObject::realm_execution_context()
 {
     // NOTE: All environment settings objects are created with a realm execution context, so it's stored and returned here in the base class.

Libraries/LibWeb/HTML/Scripting/Environments.h

@@ -46,6 +46,9 @@ public:
     // https://html.spec.whatwg.org/multipage/webappapis.html#concept-environment-execution-ready-flag
     bool execution_ready { false };
 
+    // https://html.spec.whatwg.org/multipage/webappapis.html#environment-discarding-steps
+    virtual void discard_environment() { }
+
 protected:
     virtual void visit_edges(Cell::Visitor&) override;
 };
@@ -115,6 +118,8 @@ public:
     [[nodiscard]] bool discarded() const { return m_discarded; }
     void set_discarded(bool b) { m_discarded = b; }
 
+    virtual void discard_environment() override;
+
 protected:
     explicit EnvironmentSettingsObject(NonnullOwnPtr<JS::ExecutionContext>);
 

Services/WebWorker/DedicatedWorkerHost.cpp

@@ -156,7 +156,9 @@ void DedicatedWorkerHost::run(GC::Ref<Web::Page> page, Web::HTML::TransferDataHo
         if (!script || !script->error_to_rethrow().is_null()) {
             // FIXME: 1. Queue a global task on the DOM manipulation task source given worker's relevant global object to fire an event named error at worker.
             // FIXME: Notify Worker parent through IPC to fire an error event at Worker
-            // FIXME 2. Run the environment discarding steps for inside settings.
+
+            // 2. Run the environment discarding steps for inside settings.
+            inside_settings->discard_environment();
 
             // 3. Abort these steps.
             dbgln("DedicatedWorkerHost: Unable to fetch script {} because {}", url, script ? script->error_to_rethrow().to_string_without_side_effects() : "script was null"_string);