Revert "Remove Expect from core library."

tests/language/deopt_inlined_function_lazy_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.
 // Test lazy deoptimization from within an inlined function.
 // VMOptions=--deoptimize_alot
 
-import "package:expect/expect.dart";
-
 call_native(x) {
   // Wrap in try to avoid inlining.
   // Use a large int so the intrinsifier does not fire.
   try { return x + 12342353257893275483274832; } finally { }
 }
 
 bar(x) {
   if (x < 0) call_native(x);
   x = 42;
   return x;
 }
 
 foo(x) {
   x = bar(x);
   return x;
 }
 
 main() {
   Expect.equals(42, foo(1));
   for (var i = 0; i < 2000; i++) foo(7);
   Expect.equals(42, foo(2));
   // Call the runtime to trigger lazy deopt with foo/bar on the stack.
   Expect.equals(42, foo(-1));
 }