LibWeb: Implement the "create" and "run" methods of ClassicScript

These correspond to "create a classic script" and "run a classic script"
from the HTML specification. :^)

Userland/Libraries/LibWeb/HTML/Scripting/ClassicScript.cpp

@@ -4,18 +4,65 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibJS/Interpreter.h>
 #include <LibWeb/HTML/Scripting/ClassicScript.h>
 
 namespace Web::HTML {
 
-NonnullRefPtr<ClassicScript> ClassicScript::create(URL base_url, RefPtr<JS::Script> script_record)
+// https://html.spec.whatwg.org/multipage/webappapis.html#creating-a-classic-script
+NonnullRefPtr<ClassicScript> ClassicScript::create(StringView source, JS::GlobalObject& global_object, URL base_url, MutedErrors muted_errors)
 {
-    return adopt_ref(*new ClassicScript(move(base_url), move(script_record)));
+    // 1. If muted errors was not provided, let it be false. (NOTE: This is taken care of by the default argument.)
+
+    // 2. If muted errors is true, then set baseURL to about:blank.
+    if (muted_errors == MutedErrors::Yes)
+        base_url = "about:blank";
+
+    // FIXME: 3. If scripting is disabled for settings, then set source to the empty string.
+
+    // 4. Let script be a new classic script that this algorithm will subsequently initialize.
+    auto script = adopt_ref(*new ClassicScript(move(base_url)));
+
+    // FIXME: 5. Set script's settings object to settings.
+
+    // 6. Set script's base URL to baseURL. (NOTE: This was already done when constructing.)
+
+    // FIXME: 7. Set script's fetch options to options.
+
+    // 8. Set script's muted errors to muted errors.
+    script->m_muted_errors = muted_errors;
+
+    // FIXME: 9. Set script's parse error and error to rethrow to null.
+
+    // 10. Let result be ParseScript(source, settings's Realm, script).
+    auto result = JS::Script::parse(source, global_object);
+
+    // FIXME: 11. If result is a list of errors, then:
+    //            1. Set script's parse error and its error to rethrow to result[0].
+    //            2. Return script.
+
+    // 12. Set script's record to result.
+    script->m_script_record = move(result);
+
+    // 13. Return script.
+    return script;
 }
 
-ClassicScript::ClassicScript(URL base_url, RefPtr<JS::Script> script_record)
+// https://html.spec.whatwg.org/multipage/webappapis.html#run-a-classic-script
+JS::Value ClassicScript::run(RethrowErrors rethrow_errors)
+{
+    (void)rethrow_errors;
+
+    auto interpreter = JS::Interpreter::create_with_existing_global_object(m_script_record->global_object());
+    interpreter->run(interpreter->global_object(), m_script_record->parse_node());
+    auto& vm = interpreter->vm();
+    if (vm.exception())
+        vm.clear_exception();
+    return vm.last_value();
+}
+
+ClassicScript::ClassicScript(URL base_url)
     : Script(move(base_url))
-    , m_script_record(move(script_record))
 {
 }