Updated the early close test, to use a Socket that we can close at any time.

tests/standalone/src/io/HttpServerEarlyClientCloseTest.dart

+#import("dart:io");
+#import("dart:isolate");
+
+void sendData(List<int> data, int port) {
+  Socket socket = new Socket("127.0.0.1", port);
+  socket.onConnect = () {
+    socket.onData = () {
+      Expect.fail("No data response was expected");
+    };
+    socket.outputStream.onNoPendingWrites = () {
+      socket.close(false);
+    };
+    socket.outputStream.write(data);
+  };
+}
+
+class EarlyCloseTest {
+  EarlyCloseTest(Object this.data,
+                 String this.exception,
+                 [bool this.expectRequest = false]);
+
+  Future execute(HttpServer server) {
+    Completer c = new Completer();
+
+    bool calledOnRequest = false;
+    server.onRequest = (HttpRequest request, HttpResponse response) {
+      Expect.isTrue(expectRequest);
+      Expect.isFalse(calledOnRequest, "onRequest called multiple times");
+      calledOnRequest = true;
+    };
+    ReceivePort port = new ReceivePort();
+    server.onError = (Exception error) {
+      Expect.equals(exception, error.message);
+      calledOnRequest = true;  // onRequest is not allowed after onError.
+      port.close();
+      c.complete(null);
+    };
+
+    List<int> d;
+    if (data is List<int>) d = data;
+    if (data is String) d = data.charCodes();
+    if (d == null) Expect.fail("Invalid data");
+    sendData(d, server.port);
+
+    return c.future;
+  }
+
+  final Object data;
+  final String exception;
+  final bool expectRequest;
+}
+
+void testEarlyClose() {
+  List<EarlyCloseTest> tests = new List<EarlyCloseTest>();
+  void add(Object data, String exception, [bool expectRequest = false]) {
+    tests.add(new EarlyCloseTest(data, exception, expectRequest));
+  }
+  // The empty packet is valid.
+
+  // Close while sending header
+  add("G", "Connection closed before header was received");
+  add("GET /", "Failed to parse HTTP");
+  add("GET / HTTP/1.1", "Failed to parse HTTP");
+  add("GET / HTTP/1.1\r\n", "Failed to parse HTTP");
+
+  // Close while sending content
+  add("GET / HTTP/1.1\r\nContent-Length: 100\r\n\r\n",
+      "Failed to parse HTTP",
+      expectRequest: true);
+  add("GET / HTTP/1.1\r\nContent-Length: 100\r\n\r\n1",
+      "Failed to parse HTTP",
+      expectRequest: true);
+
+
+  HttpServer server = new HttpServer();
+  server.listen("127.0.0.1", 0);
+  void runTest(Iterator it) {
+    if (it.hasNext()) {
+      it.next().execute(server).then((_) => runTest(it));
+    } else {
+      server.close();
+    }
+  }
+  runTest(tests.iterator());
+}
+
+void main() {
+  testEarlyClose();
+}