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

sdk/lib/_internal/pub/lib/src/command/serve.dart

Index: sdk/lib/_internal/pub/lib/src/command/serve.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command/serve.dart b/sdk/lib/_internal/pub/lib/src/command/serve.dart
index d2aa3ebd4db3de8c32f3ffafe76ac186668ac4aa..ad6a567b6f9fcfe3eeae49286e2efdde503f1ead 100644
--- a/sdk/lib/_internal/pub/lib/src/command/serve.dart
+++ b/sdk/lib/_internal/pub/lib/src/command/serve.dart
@@ -27,9 +27,19 @@ class ServeCommand extends PubCommand {
 
   PubPackageProvider _provider;
 
+  String get hostname => commandOptions['hostname'];
+
   ServeCommand() {
     commandParser.addOption('port', defaultsTo: '8080',
         help: 'The port to listen on.');
+
+    // A hidden option for the tests to work around a bug in some of the OS X
+    // bots where "localhost" very rarely resolves to the IPv4 loopback address
+    // instead of IPv6 (or vice versa). The tests will always set this to
+    // 127.0.0.1.
+    commandParser.addOption('hostname',
+                            defaultsTo: 'localhost',
+                            hide: true);
   }
 
   Future onRun() {
@@ -44,7 +54,7 @@ class ServeCommand extends PubCommand {
 
     return ensureLockFileIsUpToDate()
         .then((_) => entrypoint.loadPackageGraph())
-        .then((graph) => barback.createServer("localhost", port, graph))
+        .then((graph) => barback.createServer(hostname, port, graph))
         .then((server) {
       /// This completer is used to keep pub running (by not completing) and
       /// to pipe fatal errors to pub's top-level error-handling machinery.
@@ -85,7 +95,7 @@ class ServeCommand extends PubCommand {
       });
 
       log.message("Serving ${entrypoint.root.name} "
-          "on http://localhost:${server.port}");
+          "on http://$hostname:${server.port}");
 
       return completer.future;
     });