Cleanup 1: split parts into their own libraries, remove unused imports

pkg/compiler/lib/src/helpers/stats.dart

 // Copyright (c) 2014, 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.
 
-part of dart2js.helpers;
+import 'dart:async' show
+    EventSink;
+import 'dart:collection';
+import 'dart:convert';
+
+import '../../compiler.dart';
+import '../common.dart';
+import '../compiler.dart' show
+    Compiler;
+import '../util/util.dart';
+
 
 // Helper methods for statistics.
 
 /// Current stats collector. Use [enableStatsOutput] to enable recording of
 /// stats.
 Stats get stats {
   enableDebugMode();
   if (_stats == null) {
     _stats = const Stats();
   }
@@ skipping 763 matching lines @@
 /// Returns a new map in which the keys of [map] are sorted using [compare].
 /// If [compare] is null, the keys must be [Comparable].
 Map sortMap(Map map, [int compare(a,b)]) {
   List keys = map.keys.toList();
   keys.sort(compare);
   Map sortedMap = new Map();
   keys.forEach((k) => sortedMap[k] = map[k]);
   return sortedMap;
 }