LibWeb+WebDriver: Support running headless WebDriver sessions

This adds an "extension capability" for clients to indicate that a
headless browser should be used for the session.

Userland/Services/WebDriver/Client.cpp

@@ -151,11 +151,11 @@ Web::WebDriver::Response Client::new_session(Web::WebDriver::Parameters, JsonVal
     auto session_id = Client::s_next_session_id++;
 
     // 7. Let session be a new session with the session ID of session id.
-    NonnullOwnPtr<Session> session = make<Session>(session_id, *this);
-    auto start_result = session->start();
-    if (start_result.is_error()) {
+    Web::WebDriver::LadybirdOptions options { capabilities.as_object() };
+    auto session = make<Session>(session_id, *this, move(options));
+
+    if (auto start_result = session->start(); start_result.is_error())
         return Web::WebDriver::Error::from_code(Web::WebDriver::ErrorCode::SessionNotCreated, String::formatted("Failed to start session: {}", start_result.error().string_literal()));
-    }
 
     auto& web_content_connection = session->web_content_connection();
 

Userland/Services/WebDriver/Session.cpp

@@ -17,8 +17,9 @@
 
 namespace WebDriver {
 
-Session::Session(unsigned session_id, NonnullRefPtr<Client> client)
+Session::Session(unsigned session_id, NonnullRefPtr<Client> client, Web::WebDriver::LadybirdOptions options)
     : m_client(move(client))
+    , m_options(move(options))
     , m_id(session_id)
 {
 }
@@ -63,14 +64,26 @@ ErrorOr<void> Session::start()
     auto web_content_socket_path = String::formatted("/tmp/webdriver/session_{}_{}", getpid(), m_id);
     auto web_content_server = TRY(create_server(web_content_socket_path, promise));
 
-    char const* argv[] = {
-        "/bin/Browser",
-        "--webdriver-content-path",
-        web_content_socket_path.characters(),
-        nullptr,
-    };
+    if (m_options.headless) {
+        char const* argv[] = {
+            "/bin/headless-browser",
+            "--webdriver-ipc-path",
+            web_content_socket_path.characters(),
+            "about:blank",
+            nullptr,
+        };
 
-    m_browser_pid = TRY(Core::System::posix_spawn("/bin/Browser"sv, nullptr, nullptr, const_cast<char**>(argv), environ));
+        m_browser_pid = TRY(Core::System::posix_spawn("/bin/headless-browser"sv, nullptr, nullptr, const_cast<char**>(argv), environ));
+    } else {
+        char const* argv[] = {
+            "/bin/Browser",
+            "--webdriver-content-path",
+            web_content_socket_path.characters(),
+            nullptr,
+        };
+
+        m_browser_pid = TRY(Core::System::posix_spawn("/bin/Browser"sv, nullptr, nullptr, const_cast<char**>(argv), environ));
+    }
 
     // FIXME: Allow this to be more asynchronous. For now, this at least allows us to propagate
     //        errors received while accepting the Browser and WebContent sockets.

Userland/Services/WebDriver/Session.h

@@ -11,6 +11,7 @@
 #include <AK/Error.h>
 #include <AK/RefPtr.h>
 #include <LibCore/Promise.h>
+#include <LibWeb/WebDriver/Capabilities.h>
 #include <LibWeb/WebDriver/Error.h>
 #include <LibWeb/WebDriver/Response.h>
 #include <WebDriver/WebContentConnection.h>
@@ -20,7 +21,7 @@ namespace WebDriver {
 
 class Session {
 public:
-    Session(unsigned session_id, NonnullRefPtr<Client> client);
+    Session(unsigned session_id, NonnullRefPtr<Client> client, Web::WebDriver::LadybirdOptions options);
     ~Session();
 
     unsigned session_id() const { return m_id; }
@@ -39,8 +40,11 @@ private:
     ErrorOr<NonnullRefPtr<Core::LocalServer>> create_server(String const& socket_path, NonnullRefPtr<ServerPromise> promise);
 
     NonnullRefPtr<Client> m_client;
+    Web::WebDriver::LadybirdOptions m_options;
+
     bool m_started { false };
     unsigned m_id { 0 };
+
     RefPtr<WebContentConnection> m_web_content_connection;
     Optional<pid_t> m_browser_pid;
 };

Userland/Services/WebDriver/main.cpp

@@ -71,6 +71,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     outln("Listening on {}:{}", ipv4_address.value(), port);
 
     TRY(Core::System::unveil("/bin/Browser", "rx"));
+    TRY(Core::System::unveil("/bin/headless-browser", "rx"));
     TRY(Core::System::unveil("/etc/timezone", "r"));
     TRY(Core::System::unveil("/res/icons", "r"));
     TRY(Core::System::unveil("/tmp/webdriver", "rwc"));