Make sure files end with exactly one new line and police this in presubmit.

test/mjsunit/regress/regress-45469.js

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 24 matching lines @@
   assertEquals(i % 3 == 2 ? null : ["x"], res, "res" + i);
 }
 
 re = /x/g;
 
 for (var i = 0; i < 15; i++) {
   assertEquals(i % 3, re.lastIndex, "testpreindex" + i);
   var res = re.test("xx");
   assertEquals(i % 3 != 2, res, "testres" + i);
 }
-
-