Change pub tests and pub local server to use ipV4 localhost by address.

sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart

Index: sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart b/sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart
index b2c8464d451cdf4467f9eb0902cc6eeb8efa3797..2f8c6653c14b8a09af17ff26b96ab7589bb4fdc1 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart
@@ -25,7 +25,7 @@ import 'dart:isolate';
 import 'dart:convert';
 import 'dart:mirrors';
 
-import 'http://localhost:<<PORT>>/packages/barback/barback.dart';
+import 'http://<<HOST_AND_PORT>>/packages/barback/barback.dart';
 
 /// Sets up the initial communication with the host isolate.
 void main() {
@@ -47,7 +47,7 @@ Iterable<Transformer> initialize(Uri uri, Map configuration) {
   var mirrors = currentMirrorSystem();
   // TODO(nweiz): look this up by name once issue 5897 is fixed.
   var transformerUri = Uri.parse(
-      'http://localhost:<<PORT>>/packages/barback/src/transformer.dart');
+      'http://<<HOST_AND_PORT>>/packages/barback/src/transformer.dart');
   var transformerClass = mirrors.libraries[transformerUri]
       .classes[const Symbol('Transformer')];
 
@@ -288,10 +288,10 @@ Future<Set<Transformer>> loadTransformers(BarbackServer server,
     TransformerId id) {
   var path = id.asset.path.replaceFirst('lib/', '');
   // TODO(nweiz): load from a "package:" URI when issue 12474 is fixed.
-  var uri = 'http://localhost:${server.port}/packages/${id.asset.package}/'
-      '$path';
+  var hostAndPort = '${server.host}:${server.port}';
+  var uri = 'http://$hostAndPort/packages/${id.asset.package}/$path';
   var code = 'import "$uri";' +
-      _TRANSFORMER_ISOLATE.replaceAll('<<PORT>>', server.port.toString());
+      _TRANSFORMER_ISOLATE.replaceAll('<<HOST_AND_PORT>>', hostAndPort);
   log.fine("Loading transformers from ${id.asset}");
   return dart.runInIsolate(code).then((sendPort) {
     return _receiveFuture(sendPort.call({