Remove deprecated mappedBy.

Committed: https://code.google.com/p/dart/source/detail?r=18575
Reverted: http://code.google.com/p/dart/source/detail?r=18576

Review URL: https://codereview.chromium.org//12212213

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@18579 260f80e4-7a28-3924-810f-c04153c831b5

pkg/serialization/lib/src/format.dart

@@ -216,7 +216,7 @@ class SimpleJsonFormat extends Format {
     } else {
       throw new SerializationException("Invalid data format");
     }
-    // Do not use mappedBy or other lazy operations for this. They do not play
+    // Do not use map or other lazy operations for this. They do not play
     // well with a function that destructively modifies its arguments.
     var newData = mapValues(data, (each) => recursivelyFixUp(each, r, result));
     result[ruleNumber].add(newData);