headless-browser: Add a flag to log the slowest 10 LibWeb tests

Useful for finding tests that take a long time to execute.

As of this commit, on macOS, we have:

Text/input/cookie.html: 1228ms
Text/input/css/transition-basics.html: 1060ms
Text/input/HTML/DedicatedWorkerGlobalScope-instanceof.html: 182ms
Text/input/WebAnimations/misc/animation-events-basic.html: 148ms
Text/input/Crypto/SubtleCrypto-deriveBits.html: 130ms
Text/input/IntersectionObserver/observe-box-inside-container-with-scrollable-overflow.html: 117ms
Text/input/navigation/attempt-navigating-object-without-a-document.html: 109ms
Text/input/css/getComputedStyle-print-all.html: 71ms
Text/input/WebAnimations/misc/animation-single-iteration-no-repeat.html: 61ms
Text/input/WebAnimations/animation-methods/updatePlaybackRate.html: 55ms

And on Linux:

Text/input/cookie.html: 1326ms
Text/input/css/transition-basics.html: 1155ms
Screenshot/text-shadow.html: 772ms
Screenshot/css-background-repeat.html: 622ms
Screenshot/object-fit-position.html: 541ms
Screenshot/css-background-position.html: 456ms
Screenshot/css-gradients.html: 451ms
Screenshot/border-radius.html: 400ms
Screenshot/svg-radialGradient.html: 398ms
Text/input/css/getComputedStyle-print-all.html: 325ms

Ladybird/Headless/Application.cpp

@@ -34,6 +34,7 @@ void Application::create_platform_arguments(Core::ArgsParser& args_parser)
     args_parser.add_option(resources_folder, "Path of the base resources folder (defaults to /res)", "resources", 'r', "resources-root-path");
     args_parser.add_option(is_layout_test_mode, "Enable layout test mode", "layout-test-mode");
     args_parser.add_option(rebaseline, "Rebaseline any executed layout or text tests", "rebaseline");
+    args_parser.add_option(log_slowest_tests, "Log the tests with the slowest run times", "log-slowest-tests");
 }
 
 void Application::create_platform_options(WebView::ChromeOptions& chrome_options, WebView::WebContentOptions& web_content_options)

Ladybird/Headless/Application.h

@@ -59,6 +59,7 @@ public:
     ByteString test_glob;
     bool test_dry_run { false };
     bool rebaseline { false };
+    bool log_slowest_tests { false };
 
 private:
     RefPtr<Requests::RequestClient> m_request_client;

Ladybird/Headless/Test.cpp

@@ -8,6 +8,7 @@
 #include <AK/ByteString.h>
 #include <AK/Enumerate.h>
 #include <AK/LexicalPath.h>
+#include <AK/QuickSort.h>
 #include <AK/Vector.h>
 #include <Ladybird/Headless/Application.h>
 #include <Ladybird/Headless/HeadlessWebView.h>
@@ -426,7 +427,9 @@ ErrorOr<void> run_tests(Core::AnonymousBuffer const& theme, Gfx::IntSize window_
             auto index = current_test++;
             if (index >= tests.size())
                 return;
+
             auto& test = tests[index];
+            test.start_time = UnixDateTime::now();
 
             if (is_tty) {
                 // Keep clearing and reusing the same line if stdout is a TTY.
@@ -449,6 +452,8 @@ ErrorOr<void> run_tests(Core::AnonymousBuffer const& theme, Gfx::IntSize window_
         };
 
         view.test_promise().when_resolved([&, run_next_test](auto result) {
+            result.test.end_time = UnixDateTime::now();
+
             switch (result.result) {
             case TestResult::Pass:
                 ++pass_count;
@@ -490,6 +495,24 @@ ErrorOr<void> run_tests(Core::AnonymousBuffer const& theme, Gfx::IntSize window_
     for (auto const& non_passing_test : non_passing_tests)
         outln("{}: {}", test_result_to_string(non_passing_test.result), non_passing_test.test.input_path);
 
+    if (app.log_slowest_tests) {
+        auto tests_to_print = min(10uz, tests.size());
+        outln("\nSlowest {} tests:", tests_to_print);
+
+        quick_sort(tests, [&](auto const& lhs, auto const& rhs) {
+            auto lhs_duration = lhs.end_time - lhs.start_time;
+            auto rhs_duration = rhs.end_time - rhs.start_time;
+            return lhs_duration > rhs_duration;
+        });
+
+        for (auto const& test : tests.span().trim(tests_to_print)) {
+            auto name = LexicalPath::relative_path(test.input_path, app.test_root_path);
+            auto duration = test.end_time - test.start_time;
+
+            outln("{}: {}ms", name, duration.to_milliseconds());
+        }
+    }
+
     if (app.dump_gc_graph) {
         app.for_each_web_view([&](auto& view) {
             if (auto path = view.dump_gc_graph(); path.is_error())

Ladybird/Headless/Test.h

@@ -12,6 +12,7 @@
 #include <AK/RefPtr.h>
 #include <AK/String.h>
 #include <AK/StringView.h>
+#include <AK/Time.h>
 #include <LibCore/Forward.h>
 #include <LibCore/Promise.h>
 #include <LibGfx/Forward.h>
@@ -56,6 +57,9 @@ struct Test {
     ByteString input_path {};
     ByteString expectation_path {};
 
+    UnixDateTime start_time {};
+    UnixDateTime end_time {};
+
     String text {};
     bool did_finish_test { false };
     bool did_finish_loading { false };