Combine unmodifiable_collection package into collection_helpers.

pkg/collection_helpers/lib/algorithms.dart

 // Copyright (c) 2013, 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.
 
 /**
  * Operations on collections.
  */
-library dart.collection_helper.algorithms;
+library dart.collection_helpers.algorithms;
 
 import "dart:math" show Random;
 
 /** Version of [binarySearch] optimized for comparable keys */
 int _comparableBinarySearch(List<Comparable> list, Comparable key) {
   int min = 0;
   int max = list.length;
   while (min < max) {
     int mid = min + ((max - min) >> 1);
     var element = list[mid];
@@ skipping 273 matching lines @@
       target.setRange(targetOffset, targetOffset + (firstEnd - cursor1),
           firstList, cursor1);
       return;
     }
   }
   // First list empties first. Reached by break above.
   target[targetOffset++] = secondElement;
   target.setRange(targetOffset, targetOffset + (secondEnd - cursor2),
       secondList, cursor2);
 }