Make corelib_strong tests strong-mode compliant

tests/corelib_strong/iterable_skip_test.dart

Index: tests/corelib_strong/iterable_skip_test.dart
diff --git a/tests/corelib_strong/iterable_skip_test.dart b/tests/corelib_strong/iterable_skip_test.dart
index 59d604dbf6c5328e0b953a1ba48195e387741052..b9d97aafcb0d12da35d004957eb7e34425ade074 100644
--- a/tests/corelib_strong/iterable_skip_test.dart
+++ b/tests/corelib_strong/iterable_skip_test.dart
@@ -215,17 +215,17 @@ main() {
   Expect.isFalse(it.moveNext());
   Expect.isNull(it.current);
 
-  skip0 = set2.skip(0);
-  it = skip0.iterator;
-  Expect.isNull(it.current);
-  Expect.isFalse(it.moveNext());
-  Expect.isNull(it.current);
+  var dynamicSkip0 = set2.skip(0);

[Leaf, 2017/02/08 02:03:49]

Alternatively, could make the set2 declaration be Set<int>, since it doesn't
look like the type is material.  I'm fine either way.

+  var dynamicIt = dynamicSkip0.iterator;
+  Expect.isNull(dynamicIt.current);
+  Expect.isFalse(dynamicIt.moveNext());
+  Expect.isNull(dynamicIt.current);
 
-  skip1 = set2.skip(1);
-  it = skip1.iterator;
-  Expect.isNull(it.current);
-  Expect.isFalse(it.moveNext());
-  Expect.isNull(it.current);
+  var dynamicSkip1 = set2.skip(1);
+  dynamicIt = dynamicSkip1.iterator;
+  Expect.isNull(dynamicIt.current);
+  Expect.isFalse(dynamicIt.moveNext());
+  Expect.isNull(dynamicIt.current);
 
   testSkipTake(Iterable input, int skip, int take) {
     List expected = [];