Remove Expect from core library.

tests/standalone/io/regress_7679_test.dart

Index: tests/standalone/io/regress_7679_test.dart
diff --git a/tests/standalone/io/regress_7679_test.dart b/tests/standalone/io/regress_7679_test.dart
index b13c249cd765b5303962bb6b5c22b23ee71020eb..dba91ed9ad414a403fb210fd6fd742a586d02430 100644
--- a/tests/standalone/io/regress_7679_test.dart
+++ b/tests/standalone/io/regress_7679_test.dart
@@ -2,6 +2,7 @@
 // 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";
 import 'dart:io';
 
 main() {
@@ -10,6 +11,14 @@ main() {
   script.writeAsStringSync("""
 import 'dart:io';
 
+class Expect {
+  static void isTrue(var x) {
+    if (!identical(x, true)) {
+      throw new Error("Not identical");
+    }
+  }
+}
+
 main() {
   Directory d = new Directory('a');
   d.create(recursive: true).then((_) {