Remove Expect from core library.

tests/compiler/dart2js_extra/bailout_on_break_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";
+
 class A {
   operator+(arg) => 42;
 }
 
 get42() => 42;
 getNonInt() => new A();
 use(x) => x;
 
 void testInWhileLoop() {
   var c = get42();
@@ skipping 109 matching lines @@
 main() {
   testInWhileLoop();
   testInDoWhileLoop();
   testInForLoop();
   testInNestedWhileLoop();
   testInNestedWhileLoop2();
   testInNestedWhileLoop3();
   testLabeledIf();
   testLabeledIf2();
 }