Optimize some collection operations.

runtime/lib/array.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.
 
 
 // TODO(srdjan): Use shared array implementation.
 class _List<E> implements List<E> {
   static final int _classId = (new _List(0))._cid;
 
   factory _List(length) native "List_allocate";
@@ skipping 59 matching lines @@
     }
     if (end < start || end > this.length) {
       throw new RangeError.range(end, start, this.length);
     }
     int length = end - start;
     if (length == 0) return;
 
     if (iterable is _List) {
       _copyFromObjectArray(iterable, skipCount, start, length);
     } else {
-      List otherList;
-      int otherStart;
       if (iterable is List) {
-        otherList = iterable;
-        otherStart = skipCount;
+        Arrays.copy(iterable, skipCount, this, start, length);
       } else {
-        otherList =
-            iterable.skip(skipCount).take(length).toList(growable: false);
-        otherStart = 0;
+        Iterator it = iterable.iterator;
+        while (skipCount > 0) {
+          if (!it.moveNext()) return;
+          skipCount--;
+        }
+        for (int i = start; i < end; i++) {
+          if (!it.moveNext()) return;
+          this[i] = it.current;
+        }
       }
-      Arrays.copy(otherList, otherStart, this, start, length);
     }
   }
 
   void removeRange(int start, int end) {
     throw new UnsupportedError(
         "Cannot remove range of a non-extendable array");
   }
 
   void replaceRange(int start, int end, Iterable<E> iterable) {
     throw new UnsupportedError(
@@ skipping 457 matching lines @@
     }
     _position = _length;
     _current = null;
     return false;
   }
 
   E get current {
     return _current;
   }
 }