Fix http requests and the crash dump RPC

runtime/observatory/tests/service/crash_dump_test.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library crash_dump_test;
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+import 'package:observatory/service_io.dart';
+
+import 'test_helper.dart';
+
+Future warmup() async {
+  print('hi');
+}
+
+var tests = [
+  (VM vm) async {
+    HttpClient client = new HttpClient();
+    var request =
+        await client.getUrl(Uri.parse('$serviceHttpAddress/_getCrashDump'));
+    var response = await request.close();
+    Completer completer = new Completer();
+    StringBuffer sb = new StringBuffer();
+    response.transform(UTF8.decoder).listen((chunk) {
+      sb.write(chunk);
+    }, onDone: () => completer.complete(sb.toString()));
+    var responseString = await completer.future;
+    JSON.decode(responseString);
+  }
+];
+
+main(args) async => runVMTests(args, tests, testeeBefore:warmup);