LibWeb: Add a simple DumpLayoutTree program

This loads a page and, dumps the layout tree to stdout, and exits.

Libraries/LibWeb/DumpLayoutTree/CMakeLists.txt

@@ -0,0 +1,6 @@
+set(SOURCES
+    main.cpp
+)
+
+serenity_bin(DumpLayoutTree)
+target_link_libraries(DumpLayoutTree LibWeb)

Libraries/LibWeb/DumpLayoutTree/main.cpp

@@ -0,0 +1,34 @@
+#include <LibCore/ArgsParser.h>
+#include <LibGUI/Application.h>
+#include <LibWeb/Dump.h>
+#include <LibWeb/InProcessWebView.h>
+#include <LibWeb/Layout/InitialContainingBlockBox.h>
+#include <stdlib.h>
+
+int main(int argc, char** argv)
+{
+    auto app = GUI::Application::construct(argc, argv);
+    auto window = GUI::Window::construct();
+    window->set_title("DumpLayoutTree");
+    window->resize(800, 600);
+    window->show();
+    auto& web_view = window->set_main_widget<Web::InProcessWebView>();
+    web_view.load(URL::create_with_file_protocol(argv[1]));
+    web_view.on_load_finish = [&](auto&) {
+        auto* document = web_view.document();
+        if (!document) {
+            warnln("No document.");
+            _exit(1);
+        }
+        auto* layout_root = document->layout_node();
+        if (!layout_root) {
+            warnln("No layout tree.");
+            _exit(1);
+        }
+        StringBuilder builder;
+        Web::dump_tree(builder, *layout_root);
+        write(STDOUT_FILENO, builder.string_view().characters_without_null_termination(), builder.length());
+        _exit(0);
+    };
+    return app->exec();
+}