Add an issue reference to a TODO in barback.

R=rnystrom@google.com
BUG=

Review URL: https://codereview.chromium.org//152083007

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@32536 260f80e4-7a28-3924-810f-c04153c831b5

pkg/barback/lib/src/phase_input.dart

@@ -207,7 +207,7 @@ class PhaseInput {
         if (!transformers.contains(transform.transformer)) return false;
 
         // TODO(rnystrom): Catch all errors from isPrimary() and redirect to
-        // results.
+        // results (issue 16162).
         return transform.transformer.isPrimary(asset);
       }).then((isPrimary) {
         if (isPrimary) return;