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

pkg/compiler/lib/src/helpers/trace.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 '../common.dart';
+import '../util/util.dart';
 
 /// Function signature for [trace].
 typedef void Trace(String message,
                    {bool condition(String stackTrace),
                     int limit,
                     bool throwOnPrint});
 
 /**
  * Helper method for printing stack traces for debugging.
  *
@@ skipping 337 matching lines @@
   }
   for (int index = text.length ; index < intendedLength ; index ++) {
     int dotsIndex = index % dotsLength;
     sb.write(dots.substring(dotsIndex, dotsIndex + 1));
   }
   if (padLeft) {
     sb.write(text);
   }
   return sb.toString();
 }