Support for stack traces in catch blocks.

frog/leg/lib/js_helper.dart

 // Copyright (c) 2012, 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.
 
 #library('js_helper');
 
 #import('coreimpl.dart');
 
 #source('date_helper.dart');
 #source('regexp_helper.dart');
@@ skipping 1285 matching lines @@
       }
     }
   } else if (JS('bool', @'$0 instanceof RangeError', ex)) {
     var message = JS('String', @'$0.message', ex);
     if (message.contains('call stack')) {
       return new StackOverflowException();
     }
   }
   return ex;
 }
+
+class StackTrace {
+  var stack;
+  StackTrace(this.stack);
+  String toString() => stack != null ? stack : '';
+}
+
+/**
+ * Called by generated code to fetch the stack trace from an
+ * exception.
+ */
+StackTrace getTraceFromException(exception) {
+  return new StackTrace(JS("var", @"$0.stack", exception));
+}