Add a comment to refer to bug #29629.

pkg/front_end/lib/src/fasta/type_inference/type_constraint_gatherer.dart

Index: pkg/front_end/lib/src/fasta/type_inference/type_constraint_gatherer.dart
diff --git a/pkg/front_end/lib/src/fasta/type_inference/type_constraint_gatherer.dart b/pkg/front_end/lib/src/fasta/type_inference/type_constraint_gatherer.dart
index 96fcea43a65c6834635f85b45b3783485d88c269..fbc3a0789b2f05e50f5aacf5861505c66fb1f175 100644
--- a/pkg/front_end/lib/src/fasta/type_inference/type_constraint_gatherer.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_constraint_gatherer.dart
@@ -328,7 +328,7 @@ class TypeConstraintGatherer {
     // TODO(paulberry): in imitation of analyzer, we're checking the bounds as
     // we build up the substitutions.  But I don't think that's correct--I think
     // we should build up both substitutions completely before checking any
-    // bounds.
+    // bounds.  See dartbug.com/29629.
     for (int i = 0; i < count; i++) {
       TypeParameter pFresh = new TypeParameter(params2[i].name);
       DartType variableFresh = new TypeParameterType(pFresh);