Attach source range information to parsed YAML nodes.

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

Index: sdk/lib/_internal/pub/lib/src/barback.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback.dart b/sdk/lib/_internal/pub/lib/src/barback.dart
index af5e0c45927b8597c40d748283ef9c076dd8d816..80152072c88ee974c7a9474738f10c7b1daffe40 100644
--- a/sdk/lib/_internal/pub/lib/src/barback.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback.dart
@@ -140,6 +140,7 @@ class TransformerId {
     if (configuration == null) {
       configuration = {};
     } else {
+      configuration = new Map.from(configuration);

[Bob Nystrom, 2014/06/03 00:33:14]

Document this.

Also, a nit, but can you add a blank line after this? I tend to prefer comment
lines have a blank line above them.

[nweiz, 2014/06/03 02:03:21]

Done.

       // Pull out the exclusions/inclusions.
       includes = parseField("\$include");
       excludes = parseField("\$exclude");