fix analyzer failures

tests/standalone/io/http_proxy_test.dart

Index: tests/standalone/io/http_proxy_test.dart
diff --git a/tests/standalone/io/http_proxy_test.dart b/tests/standalone/io/http_proxy_test.dart
index 9a921078420cadbae8ffb5aef8cad7869ee28fe7..70a7f8cf4e88d6e61c82c9d272b7bb47f6712847 100644
--- a/tests/standalone/io/http_proxy_test.dart
+++ b/tests/standalone/io/http_proxy_test.dart
@@ -2,9 +2,9 @@
 // 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.
 
+import "package:convert/convert.dart";
 import "package:crypto/crypto.dart";
 import "package:expect/expect.dart";
-import "package:path/path.dart";
 import "dart:async";
 import "dart:io";
 import 'dart:convert';
@@ -109,17 +109,6 @@ class ProxyServer {
     authScheme = "Basic";
   }
 
-  void useDigestAuthentication(String username, String password) {
-    this.username = username;
-    this.password = password;
-    authScheme = "Digest";
-
-    // Calculate ha1.
-    var hasher = new MD5();
-    hasher.add("${username}:${realm}:${password}".codeUnits);
-    ha1 = CryptoUtils.bytesToHex(hasher.close());
-  }
-
   basicAuthenticationRequired(request) {
     request.fold(null, (x, y) {}).then((_) {
       var response = request.response;
@@ -206,20 +195,17 @@ class ProxyServer {
               }
               Expect.isNotNull(header.parameters["response"]);
 
-              var hasher = new MD5();
-              hasher.add("${request.method}:${uri}".codeUnits);
-              var ha2 = CryptoUtils.bytesToHex(hasher.close());
+              var digest = md5.convert("${request.method}:${uri}".codeUnits);
+              var ha2 = hex.encode(digest.bytes);
 
-              var x;
-              hasher = new MD5();
               if (qop == null || qop == "" || qop == "none") {
-                hasher.add("$ha1:${nonce}:$ha2".codeUnits);
+                digest = md5.convert("$ha1:${nonce}:$ha2".codeUnits);
               } else {
-                hasher.add(
+                digest = md5.convert(
                     "$ha1:${nonce}:${nc}:${cnonce}:${qop}:$ha2".codeUnits);
               }
-              Expect.equals(CryptoUtils.bytesToHex(hasher.close()),
-                            header.parameters["response"]);
+              Expect.equals(hex.encode(digest.bytes),
+                  header.parameters["response"]);
 
               // Add a bogus Proxy-Authentication-Info for testing.
               var info = 'rspauth="77180d1ab3d6c9de084766977790f482", '