Make List.skip, List.take and List.reversed return Iterables, not Lists.

tests/corelib/iterable_skip_test.dart

Index: tests/corelib/iterable_skip_test.dart
diff --git a/tests/corelib/iterable_skip_test.dart b/tests/corelib/iterable_skip_test.dart
index fff6db71999bed5a428a9b3414480dc9b7c18ec2..2889c9ce27ff7992533b0b26ba1e84a3b2a0738e 100644
--- a/tests/corelib/iterable_skip_test.dart
+++ b/tests/corelib/iterable_skip_test.dart
@@ -13,7 +13,7 @@ main() {
   Set set2 = new Set();
 
   Iterable<int> skip0 = list1.skip(0);
-  Expect.isTrue(skip0 is List);
+  Expect.isTrue(skip0 is! List);
   Iterator<int> it = skip0.iterator;
   Expect.isNull(it.current);
   Expect.isTrue(it.moveNext());
@@ -26,8 +26,8 @@ main() {
   Expect.isNull(it.current);
 
   Iterable<int> skip1 = list1.skip(1);
-  Expect.isTrue(skip1 is List);
-  Expect.isTrue(skip1.skip(2).skip(1) is List);
+  Expect.isTrue(skip1 is! List);
+  Expect.isTrue(skip1.skip(2).skip(1) is! List);
   it = skip1.iterator;
   Expect.isNull(it.current);
   Expect.isTrue(it.moveNext());
@@ -38,8 +38,8 @@ main() {
   Expect.isNull(it.current);
 
   Iterable<int> skip2 = list1.skip(2);
-  Expect.isTrue(skip2 is List);
-  Expect.isTrue(skip2.skip(2).skip(1) is List);
+  Expect.isTrue(skip2 is! List);
+  Expect.isTrue(skip2.skip(2).skip(1) is! List);
   it = skip2.iterator;
   Expect.isNull(it.current);
   Expect.isTrue(it.moveNext());
@@ -48,16 +48,16 @@ main() {
   Expect.isNull(it.current);
 
   Iterable<int> skip3 = list1.skip(3);
-  Expect.isTrue(skip3 is List);
-  Expect.isTrue(skip3.skip(2).skip(1) is List);
+  Expect.isTrue(skip3 is! List);
+  Expect.isTrue(skip3.skip(2).skip(1) is! List);
   it = skip3.iterator;
   Expect.isNull(it.current);
   Expect.isFalse(it.moveNext());
   Expect.isNull(it.current);
 
   Iterable<int> skip4 = list1.skip(4);
-  Expect.isTrue(skip4 is List);
-  Expect.isTrue(skip4.skip(2).skip(1) is List);
+  Expect.isTrue(skip4 is! List);
+  Expect.isTrue(skip4.skip(2).skip(1) is! List);
   it = skip4.iterator;
   Expect.isNull(it.current);
   Expect.isFalse(it.moveNext());
@@ -102,8 +102,8 @@ main() {
   Expect.isNull(it.current);
 
   skip0 = list2.skip(0);
-  Expect.isTrue(skip0 is List);
-  Expect.isTrue(skip0.skip(2).skip(1) is List);
+  Expect.isTrue(skip0 is! List);
+  Expect.isTrue(skip0.skip(2).skip(1) is! List);
   it = skip0.iterator;
   Expect.isNull(it.current);
   Expect.isTrue(it.moveNext());
@@ -114,8 +114,8 @@ main() {
   Expect.isNull(it.current);
 
   skip1 = list2.skip(1);
-  Expect.isTrue(skip1 is List);
-  Expect.isTrue(skip1.skip(2).skip(1) is List);
+  Expect.isTrue(skip1 is! List);
+  Expect.isTrue(skip1.skip(2).skip(1) is! List);
   it = skip1.iterator;
   Expect.isNull(it.current);
   Expect.isTrue(it.moveNext());
@@ -124,32 +124,32 @@ main() {
   Expect.isNull(it.current);
 
   skip2 = list2.skip(2);
-  Expect.isTrue(skip2 is List);
-  Expect.isTrue(skip2.skip(2).skip(1) is List);
+  Expect.isTrue(skip2 is! List);
+  Expect.isTrue(skip2.skip(2).skip(1) is! List);
   it = skip2.iterator;
   Expect.isNull(it.current);
   Expect.isFalse(it.moveNext());
   Expect.isNull(it.current);
 
   skip3 = list2.skip(3);
-  Expect.isTrue(skip3 is List);
-  Expect.isTrue(skip3.skip(2).skip(1) is List);
+  Expect.isTrue(skip3 is! List);
+  Expect.isTrue(skip3.skip(2).skip(1) is! List);
   it = skip3.iterator;
   Expect.isNull(it.current);
   Expect.isFalse(it.moveNext());
   Expect.isNull(it.current);
 
   Iterable<String> skip02 = list3.skip(0);
-  Expect.isTrue(skip02 is List);
-  Expect.isTrue(skip02.skip(2).skip(1) is List);
+  Expect.isTrue(skip02 is! List);
+  Expect.isTrue(skip02.skip(2).skip(1) is! List);
   Iterator<String> it2 = skip02.iterator;
   Expect.isNull(it2.current);
   Expect.isFalse(it2.moveNext());
   Expect.isNull(it2.current);
 
   Iterable<String> skip12 = list3.skip(1);
-  Expect.isTrue(skip12 is List);
-  Expect.isTrue(skip12.skip(2).skip(1) is List);
+  Expect.isTrue(skip12 is! List);
+  Expect.isTrue(skip12.skip(2).skip(1) is! List);
   it2 = skip12.iterator;
   Expect.isNull(it2.current);
   Expect.isFalse(it2.moveNext());