Log exceptions caught in polymer expressions

pkg/polymer_expressions/lib/polymer_expressions.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * A binding delegate used with Polymer elements that
  * allows for complex binding expressions, including
  * property access, function invocation,
  * list/map indexing, and two-way filtering.
  *
@@ skipping 115 matching lines @@
     }
     notifyPropertyChange(#value, oldValue, _value);
   }
 
   @reflectable get value => _value;
 
   @reflectable set value(v) {
     try {
       assign(_expr, v, _scope);
     } on EvalException catch (e) {
-      // silently swallow binding errors
+      _logger.warning("Error evaluating expression '$_expr': ${e.message}");
     }
   }
 }