Ladybird: Port over ConsoleWidget from the SerenityOS Browser

While this adds a fair bit of widget code, we're also increasing code
sharing by using the same bits in WebContentClient for interacting with
the JS console.

That said, we should look for more ways to share code here.

Ladybird/ConsoleWidget.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2020, Hunter Salyer <thefalsehonesty@gmail.com>
+ * Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/String.h>
+#include <AK/Vector.h>
+#include <QWidget>
+
+class QLineEdit;
+class QTextEdit;
+
+namespace Ladybird {
+
+class ConsoleWidget final : public QWidget {
+    Q_OBJECT
+public:
+    ConsoleWidget();
+    virtual ~ConsoleWidget() = default;
+
+    void notify_about_new_console_message(i32 message_index);
+    void handle_console_messages(i32 start_index, Vector<String> const& message_types, Vector<String> const& messages);
+    void print_source_line(StringView);
+    void print_html(StringView);
+    void reset();
+
+    Function<void(String const&)> on_js_input;
+    Function<void(i32)> on_request_messages;
+
+private:
+    void request_console_messages();
+    void clear_output();
+
+    QTextEdit* m_output_view { nullptr };
+    QLineEdit* m_input { nullptr };
+
+    i32 m_highest_notified_message_index { -1 };
+    i32 m_highest_received_message_index { -1 };
+    bool m_waiting_for_messages { false };
+};
+
+}