Revert "Add reduce to Collection."

tests/corelib/collection_test.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.
-
-class CollectionTest {
-  CollectionTest(Collection collection) {
-    testReduce(collection);
-  }
-
-  void testReduce(Collection collection) {
-    Expect.equals(28, collection.reduce(0, (prev, element) => prev + element));
-    Expect.equals(
-        3024, collection.reduce(1, (prev, element) => prev * element));
-  }
-}
-
-
-main() {
-  final TEST_ELEMENTS = const [4, 2, 6, 7, 9];
-  // Const list.
-  new CollectionTest(TEST_ELEMENTS);
-
-  // Fixed size list.
-  var fixedList = new List(TEST_ELEMENTS.length);
-  for (int i = 0; i < TEST_ELEMENTS.length; i++) {
-    fixedList[i] = TEST_ELEMENTS[i];
-  }
-  new CollectionTest(fixedList);
-
-  // Dynamic size list.
-  new CollectionTest(new List.from(TEST_ELEMENTS));
-
-  // Dynamic size set.
-  new CollectionTest(new Set.from(TEST_ELEMENTS));
-}