headless-browser: Centralize test timeouts and up default to 30 seconds

We're seeing timeouts for WebWorker based tests in some CI runs. It's
possible that these are legitimate timeouts, so bump the default timeout
to 30sec. When porting the test runner to run on CI, Andreas had to bump
the test timeout from 5 seconds to 10, to 15. It's likely that loading
our ASAN/UBSAN binaries on slow CI machines takes a significant amount
of time. Tests that use the new WebWorker process are spawning yet
another process that needs to load LibWeb and all its dependencies.

Userland/Utilities/headless-browser.cpp

@@ -50,6 +50,8 @@
 #    include <Ladybird/Utilities.h>
 #endif
 
+constexpr int DEFAULT_TIMEOUT_MS = 30000; // 30sec
+
 class HeadlessWebContentView final : public WebView::ViewImplementation {
 public:
     static ErrorOr<NonnullOwnPtr<HeadlessWebContentView>> create(Core::AnonymousBuffer theme, Gfx::IntSize const& window_size, StringView web_driver_ipc_path, WebView::IsLayoutTestMode is_layout_test_mode = WebView::IsLayoutTestMode::No)
@@ -158,12 +160,12 @@ enum class TestResult {
     Timeout,
 };
 
-static ErrorOr<TestResult> run_dump_test(HeadlessWebContentView& view, StringView input_path, StringView expectation_path, TestMode mode, int timeout_in_milliseconds = 15000)
+static ErrorOr<TestResult> run_dump_test(HeadlessWebContentView& view, StringView input_path, StringView expectation_path, TestMode mode, int timeout_in_milliseconds = DEFAULT_TIMEOUT_MS)
 {
     Core::EventLoop loop;
     bool did_timeout = false;
 
-    auto timeout_timer = TRY(Core::Timer::create_single_shot(5000, [&] {
+    auto timeout_timer = TRY(Core::Timer::create_single_shot(timeout_in_milliseconds, [&] {
         did_timeout = true;
         loop.quit(0);
     }));
@@ -194,7 +196,7 @@ static ErrorOr<TestResult> run_dump_test(HeadlessWebContentView& view, StringVie
         };
     }
 
-    timeout_timer->start(timeout_in_milliseconds);
+    timeout_timer->start();
     loop.exec();
 
     if (did_timeout)
@@ -234,12 +236,12 @@ static ErrorOr<TestResult> run_dump_test(HeadlessWebContentView& view, StringVie
     return TestResult::Fail;
 }
 
-static ErrorOr<TestResult> run_ref_test(HeadlessWebContentView& view, StringView input_path, bool dump_failed_ref_tests, int timeout_in_milliseconds = 15000)
+static ErrorOr<TestResult> run_ref_test(HeadlessWebContentView& view, StringView input_path, bool dump_failed_ref_tests, int timeout_in_milliseconds = DEFAULT_TIMEOUT_MS)
 {
     Core::EventLoop loop;
     bool did_timeout = false;
 
-    auto timeout_timer = TRY(Core::Timer::create_single_shot(5000, [&] {
+    auto timeout_timer = TRY(Core::Timer::create_single_shot(timeout_in_milliseconds, [&] {
         did_timeout = true;
         loop.quit(0);
     }));
@@ -257,7 +259,7 @@ static ErrorOr<TestResult> run_ref_test(HeadlessWebContentView& view, StringView
         }
     };
 
-    timeout_timer->start(timeout_in_milliseconds);
+    timeout_timer->start();
     loop.exec();
 
     if (did_timeout)