add JsonCode example

sdk/lib/convert/json.dart

Index: sdk/lib/convert/json.dart
diff --git a/sdk/lib/convert/json.dart b/sdk/lib/convert/json.dart
index d3624ab10e7491242d7542e607ef436684b20088..08eb79708b7208cf3b0f60c258dbbbbcb0206602 100644
--- a/sdk/lib/convert/json.dart
+++ b/sdk/lib/convert/json.dart
@@ -53,8 +53,8 @@ class JsonCyclicError extends JsonUnsupportedObjectError {
  *
  * Examples:
  *
- *     var encoded = JSON.encode([1, 2, { "a": null }]);
- *     var decoded = JSON.decode('["foo", { "bar": 499 }]');
+ *    var encoded = JSON.encode([1, 2, { "a": null }]);

[Lasse Reichstein Nielsen, 2015/09/30 06:20:31]

Make sure this is indented enough. It seems to be indented only 3 if the first
space after "*" isn't counted. I'd prefer to indent it by four relative to the
other text, just to be sure (and so it's obvious that it's code-formatted).

+ *    var decoded = JSON.decode('["foo", { "bar": 499 }]');
  */
 const JsonCodec JSON = const JsonCodec();
 
@@ -65,6 +65,11 @@ typedef _ToEncodable(var o);
 /**
  * A [JsonCodec] encodes JSON objects to strings and decodes strings to
  * JSON objects.
+ *
+ * Examples:
+ *
+ *    var encoded = JSON.encode([1, 2, { "a": null }]);
+ *    var decoded = JSON.decode('["foo", { "bar": 499 }]');
  */
 class JsonCodec extends Codec<Object, String> {
   final _Reviver _reviver;