LibWeb: Add basic implementation of progress bar element

Author: https://github.com/Sauler 🔰
Commit: 21e353980f
Pull-request: https://github.com/SerenityOS/serenity/pull/12366
Reviewed-by: https://github.com/drunderscore
Reviewed-by: https://github.com/linusg
Reviewed-by: https://github.com/trflynn89 ✅

Userland/Libraries/LibWeb/HTML/HTMLProgressElement.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, the SerenityOS developers.
+ * Copyright (c) 2020-2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -16,6 +16,19 @@ public:
 
     HTMLProgressElement(DOM::Document&, QualifiedName);
     virtual ~HTMLProgressElement() override;
+
+    virtual RefPtr<Layout::Node> create_layout_node(NonnullRefPtr<CSS::StyleProperties>) override;
+
+    double value() const;
+    void set_value(double);
+
+    double max() const;
+    void set_max(double value);
+
+    double position() const;
+
+private:
+    bool is_determinate() const { return has_attribute(HTML::AttributeNames::value); }
 };
 
 }