Move Arrays class to private library.

sdk/lib/_collection_dev/arrays.dart

 // Copyright (c) 2012, 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 dart.collection;
+part of dart._collection.dev;
 
 // TODO(ngeoffray): Rename to Lists.
 class Arrays {
   static void copy(List src, int srcStart,
                    List dst, int dstStart, int count) {
-    if (srcStart == null) srcStart = 0;
-    if (dstStart == null) dstStart = 0;
-
     if (srcStart < dstStart) {
       for (int i = srcStart + count - 1, j = dstStart + count - 1;
            i >= srcStart; i--, j--) {
         dst[j] = src[i];
       }
     } else {
       for (int i = srcStart, j = dstStart; i < srcStart + count; i++, j++) {
         dst[j] = src[i];
       }
     }
@@ skipping 61 matching lines @@
     if (start < 0 ) {
       String message = "$start must be greater than or equal to 0";
       throw new RangeError(message);
     }
     if (start + length > a.length) {
       String message = "$start + $length must be in the range [0..${a.length})";
       throw new RangeError(message);
     }
   }
 }