Bind to all available loopback addresses in pub.

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

Index: sdk/lib/_internal/pub/lib/src/barback/asset_environment.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback/asset_environment.dart b/sdk/lib/_internal/pub/lib/src/barback/asset_environment.dart
index 04acfa4439a89876a2478c50ccc1ad0c93802209..5da8e629e05e33fc9399e120a4d47b0fbd778bec 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/asset_environment.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/asset_environment.dart
@@ -302,10 +302,11 @@ class AssetEnvironment {
   Future<AssetId> getAssetIdForUrl(Uri url) {
     return Future.wait(_directories.values.map((dir) => dir.server))
         .then((servers) {
-      var server = servers.firstWhere(
-          (server) => server.address.host == url.host &&
-              server.port == url.port,
-          orElse: () => null);
+      var server = servers.firstWhere((server) {
+        if (server.port != url.port) return false;
+        return isLoopback(server.address.host) == isLoopback(url.host) ||
+            server.address.host == url.host;
+      }, orElse: () => null);
       if (server == null) return null;
       return server.urlToId(url);
     });