Remove Expect from core library.

tests/lib/math/math_parse_double_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.
 
 // We temporarily test both the new math library and the old Math
 // class. This can easily be simplified once we get rid of the Math
 // class entirely.
 library math_parse_double_test;
+import "package:expect/expect.dart";
 
 void parseDoubleThrowsFormatException(str) {
   Expect.throws(() => double.parse(str), (e) => e is FormatException);
 }
 
 void main() {
   Expect.equals(499.0, double.parse("499"));
   Expect.equals(499.0, double.parse("499.0"));
   Expect.equals(499.0, double.parse("499.0"));
   Expect.equals(499.0, double.parse("+499"));
@@ skipping 92 matching lines @@
   parseDoubleThrowsFormatException(" -5. ");
   parseDoubleThrowsFormatException("1234567.e2");
   parseDoubleThrowsFormatException(" 1234567.e2 ");
   parseDoubleThrowsFormatException(" +1234567.e2 ");
   parseDoubleThrowsFormatException(" -1234567.e2 ");
   parseDoubleThrowsFormatException("+0x1234567890");
   parseDoubleThrowsFormatException("   +0x1234567890   ");
   parseDoubleThrowsFormatException("   +0x100   ");
   parseDoubleThrowsFormatException("+0x100");
 }