New Uri.parse and validation.

sdk/lib/io/http_impl.dart

Index: sdk/lib/io/http_impl.dart
diff --git a/sdk/lib/io/http_impl.dart b/sdk/lib/io/http_impl.dart
index f9fedc3410bf898fec9521989910eeef3ea6c366..b0a1d8fb35b4847b094593bf2f02beb3a96482f4 100644
--- a/sdk/lib/io/http_impl.dart
+++ b/sdk/lib/io/http_impl.dart
@@ -1674,10 +1674,10 @@ class _HttpClient implements HttpClient {
                                  String host,
                                  int port,
                                  String path) {
+    Uri uri = new Uri(scheme: "http", host: host, port: port).resolve(path);
     // TODO(sgjesse): The path set here can contain both query and
     // fragment. They should be cracked and set correctly.
-    return _openUrl(method, new Uri(
-        scheme: "http", host: host, port: port, path: path));
+    return _openUrl(method, uri);
   }
 
   Future<HttpClientRequest> openUrl(String method, Uri url) {