Move Arrays class to private library.

samples/swarm/swarm_ui_lib/observable/observable.dart

 // Copyright (c) 2011, 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.
 
 library observable;
 
 import 'dart:collection';
 
 part 'ChangeEvent.dart';
 part 'EventBatch.dart';
@@ skipping 221 matching lines @@
         removeAt(i);
         // adjust index since remove shifted elements.
         i--;
         count++;
       }
     }
     return count;
   }
 
   void copyFrom(List<T> src, int srcStart, int dstStart, int count) {
-    Arrays.copy(src, srcStart, this, dstStart, count);
+    List dst = this;
+    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];
+      }
+    }
   }
 
   void setRange(int start, int length, List from, [int startFrom = 0]) {
     throw new UnimplementedError();
   }
 
   void removeRange(int start, int length) {
     throw new UnimplementedError();
   }
 
@@ skipping 64 matching lines @@
     // Only fire on an actual change.
     if (!identical(newValue, _value)) {
       final oldValue = _value;
       _value = newValue;
       recordPropertyUpdate("value", newValue, oldValue);
     }
   }
 
   T _value;
 }