Revert "Move toString() to collection classes."

sdk/lib/collection/maps.dart

Index: sdk/lib/collection/maps.dart
diff --git a/sdk/lib/collection/maps.dart b/sdk/lib/collection/maps.dart
index 9bc7a54ede772f7d359e8448be0a5c017dfe803d..303008cc6950a815089473c7b0f4e181b89cda13 100644
--- a/sdk/lib/collection/maps.dart
+++ b/sdk/lib/collection/maps.dart
@@ -60,9 +60,6 @@ class Maps {
 
   static bool isNotEmpty(Map map) => map.keys.isNotEmpty;
 
-  // A list to identify cyclic maps during toString() calls.
-  static List _toStringList = new List();
-
   /**
    * Returns a string representing the specified map. The returned string
    * looks like this: [:'{key0: value0, key1: value1, ... keyN: valueN}':].
@@ -79,33 +76,7 @@ class Maps {
    * A typical implementation of a map's [toString] method will
    * simply return the results of this method applied to the collection.
    */
-  static String mapToString(Map m) {
-    for (int i = 0; i < _toStringList.length; i++) {
-      if (identical(_toStringList[i], m)) { return '{...}'; }
-    }
-
-    var result = new StringBuffer();
-    try {
-      _toStringList.add(m);
-      result.write('{');
-      bool first = true;
-      m.forEach((k, v) {
-        if(!first) {
-          result.write(', ');
-        }
-        first = false;
-        result.write(k);
-        result.write(': ');
-        result.write(v);
-      });
-      result.write('}');
-    } finally {
-      assert(identical(_toStringList.last, m));
-      _toStringList.removeLast();
-    }
-
-    return result.toString();
-  }
+  static String mapToString(Map m) => ToString.mapToString(m);
 
   static _id(x) => x;