LibWeb+WebContent+WebDriver: Bring session start and close up to spec

Lots of editorial spec bugs here, but these changes largely affect how
the unhandledPromptBehavior capability is handled. We also now set an
additional capability for the default User Agent string.

Libraries/LibWeb/WebDriver/UserPrompt.cpp

@@ -33,6 +33,25 @@ static constexpr PromptHandler prompt_handler_from_string(StringView prompt_hand
     VERIFY_NOT_REACHED();
 }
 
+static constexpr StringView prompt_type_to_string(PromptType prompt_type)
+{
+    switch (prompt_type) {
+    case PromptType::Alert:
+        return "alert"sv;
+    case PromptType::BeforeUnload:
+        return "beforeUnload"sv;
+    case PromptType::Confirm:
+        return "confirm"sv;
+    case PromptType::Default:
+        return "default"sv;
+    case PromptType::Prompt:
+        return "prompt"sv;
+    case PromptType::FallbackDefault:
+        return "fallbackDefault"sv;
+    }
+    VERIFY_NOT_REACHED();
+}
+
 static constexpr PromptType prompt_type_from_string(StringView prompt_type)
 {
     if (prompt_type == "alert"sv)
@@ -61,6 +80,24 @@ PromptHandlerConfiguration PromptHandlerConfiguration::deserialize(JsonValue con
     return { .handler = handler, .notify = notify };
 }
 
+// https://w3c.github.io/webdriver/#dfn-serialize-a-prompt-handler-configuration
+StringView PromptHandlerConfiguration::serialize() const
+{
+    // 1. Let serialized be configuration's handler.
+    // 2. If «"dismiss", "accept"» contains serialized, and configuration's notify is true, append " and notify" to serialized.
+    // 3. Return serialized.
+    switch (handler) {
+    case PromptHandler::Dismiss:
+        return notify == Notify::Yes ? "dismiss and notify"sv : "dismiss"sv;
+    case PromptHandler::Accept:
+        return notify == Notify::Yes ? "accept and notify"sv : "accept"sv;
+    case PromptHandler::Ignore:
+        return "ignore"sv;
+    }
+
+    VERIFY_NOT_REACHED();
+}
+
 UserPromptHandler const& user_prompt_handler()
 {
     return s_user_prompt_handler;
@@ -147,6 +184,29 @@ Response deserialize_as_an_unhandled_prompt_behavior(JsonValue value)
     return JsonValue { move(user_prompt_handler) };
 }
 
+// https://w3c.github.io/webdriver/#dfn-check-user-prompt-handler-matches
+bool check_user_prompt_handler_matches(JsonObject const& requested_prompt_handler)
+{
+    // 1. If the user prompt handler is null, return true.
+    if (!s_user_prompt_handler.has_value())
+        return true;
+
+    // 2. For each request prompt type → request handler in requested prompt handler:
+    auto result = requested_prompt_handler.try_for_each_member([&](ByteString const& request_prompt_type, JsonValue const& request_handler) -> ErrorOr<void> {
+        // 1. If the user prompt handler contains request prompt type:
+        if (auto handler = s_user_prompt_handler->get(prompt_type_from_string(request_prompt_type)); handler.has_value()) {
+            // 1. If the requested prompt handler's handler is not equal to the user prompt handler's handler, return false.
+            if (handler != PromptHandlerConfiguration::deserialize(request_handler))
+                return AK::Error::from_string_literal("Prompt handler mismatch");
+        }
+
+        return {};
+    });
+
+    // 3. Return true
+    return !result.is_error();
+}
+
 // https://w3c.github.io/webdriver/#dfn-update-the-user-prompt-handler
 void update_the_user_prompt_handler(JsonObject const& requested_prompt_handler)
 {
@@ -163,6 +223,33 @@ void update_the_user_prompt_handler(JsonObject const& requested_prompt_handler)
     });
 }
 
+// https://w3c.github.io/webdriver/#dfn-serialize-the-user-prompt-handler
+JsonValue serialize_the_user_prompt_handler()
+{
+    // 1. If the user prompt handler is null, return "dismiss and notify".
+    if (!s_user_prompt_handler.has_value())
+        return "dismiss and notify"sv;
+
+    // 2. If the user prompt handler has size 1, and user prompt handler contains "fallbackDefault", return the result
+    //    of serialize a prompt handler configuration with user prompt handler["fallbackDefault"].
+    if (s_user_prompt_handler->size() == 1) {
+        if (auto handler = s_user_prompt_handler->get(PromptType::FallbackDefault); handler.has_value())
+            return handler->serialize();
+    }
+
+    // 3. Let serialized be an empty map.
+    JsonObject serialized;
+
+    // 4. For each key → value of user prompt handler:
+    for (auto const& [key, value] : *s_user_prompt_handler) {
+        // 1. Set serialized[key] to serialize a prompt handler configuration with value.
+        serialized.set(prompt_type_to_string(key), value.serialize());
+    }
+
+    // 5. Return convert an Infra value to a JSON-compatible JavaScript value with serialized.
+    return serialized;
+}
+
 }
 
 template<>