Revert "Move Arrays class to private library."

samples/swarm/swarm_ui_lib/observable/observable.dart

Index: samples/swarm/swarm_ui_lib/observable/observable.dart
diff --git a/samples/swarm/swarm_ui_lib/observable/observable.dart b/samples/swarm/swarm_ui_lib/observable/observable.dart
index e60b8a92ee23585f7eca59833ebcd1a5cb3f3c35..794541c1dbd3c1faa5422fbb5f459d608fa64847 100644
--- a/samples/swarm/swarm_ui_lib/observable/observable.dart
+++ b/samples/swarm/swarm_ui_lib/observable/observable.dart
@@ -239,20 +239,7 @@ class ObservableList<T>
   }
 
   void copyFrom(List<T> src, int srcStart, int dstStart, int 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];
-      }
-    }
+    Arrays.copy(src, srcStart, this, dstStart, count);
   }
 
   void setRange(int start, int length, List from, [int startFrom = 0]) {