LibCore: Don't have Promise inherit from EventReceiver

This was only used for parenting promises to each other, but we can do
that with a simple vector of children.

Libraries/LibCore/Promise.h

@@ -14,13 +14,21 @@
 
 namespace Core {
 
-template<typename Result, typename TError>
+class PromiseBase
-class Promise : public EventReceiver {
+    : public RefCounted<PromiseBase>
-    C_OBJECT(Promise);
+    , public Weakable<PromiseBase> {
+public:
+    virtual ~PromiseBase() = default;
+};
 
+template<typename Result, typename TError>
+class Promise : public PromiseBase {
 public:
     using ErrorType = TError;
 
+    virtual ~Promise() = default;
+    static NonnullRefPtr<Promise> construct() { return adopt_ref(*new Promise()); }
+
     Function<ErrorOr<void>(Result&)> on_resolution;
     Function<void(ErrorType&)> on_rejection;
 
@@ -156,6 +164,8 @@ public:
         return *this;
     }
 
+    void add_child(NonnullRefPtr<PromiseBase> child) { m_children.append(move(child)); }
+
 private:
     template<typename T>
     void possibly_handle_rejection(ErrorOr<T>& result)
@@ -167,6 +177,8 @@ private:
     Promise() = default;
 
     Optional<ErrorOr<Result, ErrorType>> m_result_or_rejection;
+
+    Vector<NonnullRefPtr<PromiseBase>> m_children;
 };
 
 }

Services/WebDriver/Session.cpp

@@ -252,7 +252,7 @@ ErrorOr<NonnullRefPtr<Core::LocalServer>> Session::create_server(NonnullRefPtr<S
 
 ErrorOr<void> Session::start(LaunchBrowserCallback const& launch_browser_callback)
 {
-    auto promise = TRY(ServerPromise::try_create());
+    auto promise = ServerPromise::construct();
 
     m_web_content_socket_path = ByteString::formatted("{}/webdriver/session_{}_{}", TRY(Core::StandardPaths::runtime_directory()), getpid(), m_session_id);
     m_web_content_server = TRY(create_server(promise));

Tests/LibCore/TestLibCorePromise.cpp

@@ -15,7 +15,7 @@ TEST_CASE(promise_await_async_event)
 {
     Core::EventLoop loop;
 
-    auto promise = MUST(Core::Promise<int>::try_create());
+    auto promise = Core::Promise<int>::construct();
 
     loop.deferred_invoke([=] {
         promise->resolve(42);
@@ -30,7 +30,7 @@ TEST_CASE(promise_await_async_event_rejection)
 {
     Core::EventLoop loop;
 
-    auto promise = MUST(Core::Promise<int>::try_create());
+    auto promise = Core::Promise<int>::construct();
 
     loop.deferred_invoke([=] {
         promise->reject(AK::Error::from_string_literal("lol no"));
@@ -48,7 +48,7 @@ TEST_CASE(promise_chain_handlers)
     bool resolved = false;
     bool rejected = false;
 
-    NonnullRefPtr<Core::Promise<int>> promise = MUST(Core::Promise<int>::try_create())
+    NonnullRefPtr<Core::Promise<int>> promise = Core::Promise<int>::construct()
                                                     ->when_resolved([&](int&) -> ErrorOr<void> { resolved = true; return {}; })
                                                     .when_rejected([&](AK::Error const&) { rejected = true; });
 
@@ -68,7 +68,7 @@ TEST_CASE(infallible_promise_chain_handlers)
     bool resolved = false;
     bool rejected = false;
 
-    NonnullRefPtr<Core::Promise<int>> promise = MUST(Core::Promise<int>::try_create())
+    NonnullRefPtr<Core::Promise<int>> promise = Core::Promise<int>::construct()
                                                     ->when_resolved([&](int&) { resolved = true; })
                                                     .when_rejected([&](AK::Error const&) { rejected = true; });
 
@@ -85,7 +85,7 @@ TEST_CASE(promise_map)
 {
     Core::EventLoop loop;
 
-    auto promise = MUST(Core::Promise<int>::try_create());
+    auto promise = Core::Promise<int>::construct();
     auto mapped_promise = promise->map<int>([](int result) {
         return result * 2;
     });
@@ -103,7 +103,7 @@ TEST_CASE(promise_map_already_resolved)
 {
     Core::EventLoop loop;
 
-    auto promise = MUST(Core::Promise<int>::try_create());
+    auto promise = Core::Promise<int>::construct();
     promise->resolve(21);
 
     auto mapped_promise = promise->map<int>([](int result) {