Make corelib_strong tests strong-mode compliant

tests/corelib_strong/iterable_take_test.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.
 
 import "package:expect/expect.dart";
 
 main() {
   List<int> list1 = <int>[1, 2, 3];
   List<int> list2 = const <int>[4, 5];
   List<String> list3 = <String>[];
@@ skipping 186 matching lines @@
   Expect.isNull(it.current);
   Expect.isTrue(it.moveNext());
   Expect.isNotNull(it.current);
   Expect.isTrue(it.moveNext());
   Expect.isNotNull(it.current);
   Expect.isTrue(it.moveNext());
   Expect.isNotNull(it.current);
   Expect.isFalse(it.moveNext());
   Expect.isNull(it.current);
 
-  take0 = set2.take(0);
-  it = take0.iterator;
-  Expect.isNull(it.current);
-  Expect.isFalse(it.moveNext());
-  Expect.isNull(it.current);
+  var dynamicTake0 = set2.take(0);
+  var dynamicIt = dynamicTake0.iterator;
+  Expect.isNull(dynamicIt.current);
+  Expect.isFalse(dynamicIt.moveNext());
+  Expect.isNull(dynamicIt.current);
 
-  take1 = set2.take(1);
-  it = take1.iterator;
-  Expect.isNull(it.current);
-  Expect.isFalse(it.moveNext());
-  Expect.isNull(it.current);
+  var dynamicTake1 = set2.take(1);
+  dynamicIt = dynamicTake1.iterator;
+  Expect.isNull(dynamicIt.current);
+  Expect.isFalse(dynamicIt.moveNext());
+  Expect.isNull(dynamicIt.current);
 
   Expect.throws(() => list1.skip(-1), (e) => e is RangeError);
   Expect.throws(() => list2.skip(-1), (e) => e is RangeError);
   Expect.throws(() => list3.skip(-1), (e) => e is RangeError);
   Expect.throws(() => set1.skip(-1), (e) => e is RangeError);
   Expect.throws(() => set2.skip(-1), (e) => e is RangeError);
   Expect.throws(() => list1.map((x) => x).skip(-1), (e) => e is RangeError);
   Expect.throws(() => list2.map((x) => x).skip(-1), (e) => e is RangeError);
   Expect.throws(() => list3.map((x) => x).skip(-1), (e) => e is RangeError);
   Expect.throws(() => set1.map((x) => x).skip(-1), (e) => e is RangeError);
   Expect.throws(() => set2.map((x) => x).skip(-1), (e) => e is RangeError);
 }