Revert "Remove Expect from core library."

tests/language/import_core_prefix_test.dart

Index: tests/language/import_core_prefix_test.dart
diff --git a/tests/language/import_core_prefix_test.dart b/tests/language/import_core_prefix_test.dart
index ec237ff5b2a0580d384dac51cdcfac972348ef55..a3a7c93d767f1e16fb682d24fecab8fc32632412 100644
--- a/tests/language/import_core_prefix_test.dart
+++ b/tests/language/import_core_prefix_test.dart
@@ -4,7 +4,6 @@
 // Test explicit import of dart:core in the source code..
 
 library ImportCorePrefixTest.dart;
-import "package:expect/expect.dart";
 import "dart:core" as mycore;
 
 class Object {
@@ -31,6 +30,6 @@ void main() {
 
   var greenwich = new Map(51, 0);
   var kpao = new Map(37, -122);
-  Expect.isTrue(greenwich.isPrimeMeridian);
-  Expect.isFalse(kpao.isPrimeMeridian);
+  mycore.Expect.isTrue(greenwich.isPrimeMeridian);
+  mycore.Expect.isFalse(kpao.isPrimeMeridian);
 }