Ensure correct line endings for method_mirror_source tests.

tests/lib/mirrors/method_mirror_source_line_ending_test.dart

 // Copyright (c) 2014, 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.
 
+// Note: These tests rely on specific line endings in the source files.
+
 import "dart:mirrors";
 import "package:expect/expect.dart";
 
 import "method_mirror_source_line_ending_lf.dart";
 import "method_mirror_source_line_ending_cr.dart";
 import "method_mirror_source_line_ending_crlf.dart";
 
 main() {
   String sourceOf(Function f) => (reflect(f) as ClosureMirror).function.source;
 
   // Source does not cross line breaks.
   Expect.stringEquals('oneLineLF(x) => x;', sourceOf(oneLineLF));
   Expect.stringEquals('oneLineCR(x) => x;', sourceOf(oneLineCR));
   Expect.stringEquals('oneLineCRLF(x) => x;', sourceOf(oneLineCRLF));
 
   // Source includes line breaks.
   Expect.stringEquals('multiLineLF(y) {\n  return y + 1;\n}',
                       sourceOf(multiLineLF));
   Expect.stringEquals('multiLineCR(y) {\r  return y + 1;\r}',
                       sourceOf(multiLineCR));
   Expect.stringEquals('multiLineCRLF(y) {\r\n  return y + 1;\r\n}',
                       sourceOf(multiLineCRLF));
 
   // First and last characters separated from middle by line breaks.
   Expect.stringEquals('a\n(){\n}', sourceOf(a));
   Expect.stringEquals('b\r(){\r}', sourceOf(b));
   Expect.stringEquals('c\r\n(){\r\n}', sourceOf(c));
 }