Log exceptions caught in polymer expressions

pkg/polymer_expressions/lib/polymer_expressions.dart

Index: pkg/polymer_expressions/lib/polymer_expressions.dart
diff --git a/pkg/polymer_expressions/lib/polymer_expressions.dart b/pkg/polymer_expressions/lib/polymer_expressions.dart
index e2995e15bc6d1234827906421c883fe68f7f0e6b..02d2afb12c49b34f51f2c99a325f36e853fe17bb 100644
--- a/pkg/polymer_expressions/lib/polymer_expressions.dart
+++ b/pkg/polymer_expressions/lib/polymer_expressions.dart
@@ -133,7 +133,7 @@ class _Binding extends ChangeNotifier {
     try {
       assign(_expr, v, _scope);
     } on EvalException catch (e) {
-      // silently swallow binding errors
+      _logger.warning("Error evaluating expression '$_expr': ${e.message}");
     }
   }
 }