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

pkg/compiler/lib/src/helpers/track_map.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;
 
 /**
  * The track map is a simple wrapper around a map that keeps track
  * of the 'final' size of maps grouped by description. It allows
  * determining the distribution of sizes for a specific allocation
  * site and it can be used like this:
  *
  *    Map<String, int> map = new TrackMap<String, int>("my-map");
  *
  * After finishing the compilaton, the histogram of track map sizes
@@ skipping 88 matching lines @@
     int newLength = oldLength + delta;
     _counts[oldLength]--;
     if (newLength < _counts.length) {
       _counts[newLength]++;
     } else {
       _counts.add(1);
       assert(newLength == _counts.length - 1);
     }
   }
 }