LibWeb: Only prepare scripts on insertion if they're not parser inserted

Also updates the "inserted_into" function as per the previous commit.

Changes the FIXME, as according to the spec there is no notification
system to be notified of things such as the node becoming connected.

Instead, "becomes connected" means when the insertion steps are run,
the element is now connected when it previously wasn't.

https://html.spec.whatwg.org/multipage/infrastructure.html#becomes-connected

This is done in this PR because the insertion steps are run when the
start tag is inserted. This made it try to prepare the script too early
for inline scripts.

The order of operations in the HTML document parser ensures that
the parser document is set before the insertion steps are run.

Userland/Libraries/LibWeb/HTML/HTMLScriptElement.cpp

@@ -203,9 +203,6 @@ void HTMLScriptElement::prepare_script()
     // FIXME: Cryptographic nonce
     // FIXME: Check "integrity" attribute
     // FIXME: Check "referrerpolicy" attribute
-
-    m_parser_inserted = !!m_parser_document;
-
     // FIXME: Check fetch options
 
     if (has_attribute(HTML::AttributeNames::src)) {
@@ -254,15 +251,15 @@ void HTMLScriptElement::prepare_script()
         }
     }
 
-    if ((m_script_type == ScriptType::Classic && has_attribute(HTML::AttributeNames::src) && has_attribute(HTML::AttributeNames::defer) && m_parser_inserted && !has_attribute(HTML::AttributeNames::async))
-        || (m_script_type == ScriptType::Module && m_parser_inserted && !has_attribute(HTML::AttributeNames::async))) {
+    if ((m_script_type == ScriptType::Classic && has_attribute(HTML::AttributeNames::src) && has_attribute(HTML::AttributeNames::defer) && is_parser_inserted() && !has_attribute(HTML::AttributeNames::async))
+        || (m_script_type == ScriptType::Module && is_parser_inserted() && !has_attribute(HTML::AttributeNames::async))) {
         document().add_script_to_execute_when_parsing_has_finished({}, *this);
         when_the_script_is_ready([this] {
             m_ready_to_be_parser_executed = true;
         });
     }
 
-    else if (m_script_type == ScriptType::Classic && has_attribute(HTML::AttributeNames::src) && m_parser_inserted && !has_attribute(HTML::AttributeNames::async)) {
+    else if (m_script_type == ScriptType::Classic && has_attribute(HTML::AttributeNames::src) && is_parser_inserted() && !has_attribute(HTML::AttributeNames::async)) {
         document().set_pending_parsing_blocking_script({}, this);
         when_the_script_is_ready([this] {
             m_ready_to_be_parser_executed = true;
@@ -329,13 +326,15 @@ void HTMLScriptElement::when_the_script_is_ready(Function<void()> callback)
     m_script_ready_callback = move(callback);
 }
 
-void HTMLScriptElement::inserted_into(Node& parent)
+void HTMLScriptElement::inserted()
 {
-    // FIXME: It would be nice to have a notification for "node became connected"
-    if (is_connected()) {
-        prepare_script();
+    if (!is_parser_inserted()) {
+        // FIXME: Only do this if the element was previously not connected.
+        if (is_connected()) {
+            prepare_script();
+        }
     }
-    HTMLElement::inserted_into(parent);
+    HTMLElement::inserted();
 }
 
 }

Userland/Libraries/LibWeb/HTML/HTMLScriptElement.h

@@ -48,7 +48,9 @@ public:
     void prepare_script(Badge<HTMLDocumentParser>) { prepare_script(); }
     void execute_script();
 
-    virtual void inserted_into(Node&) override;
+    bool is_parser_inserted() const { return !!m_parser_document; }
+
+    virtual void inserted() override;
 
 private:
     void prepare_script();
@@ -59,7 +61,6 @@ private:
     WeakPtr<DOM::Document> m_preparation_time_document;
     bool m_non_blocking { false };
     bool m_already_started { false };
-    bool m_parser_inserted { false };
     bool m_from_an_external_file { false };
     bool m_script_ready { false };
     bool m_ready_to_be_parser_executed { false };