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

test/mjsunit/regress/regress-619.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 40 matching lines @@
   assertEquals(i, obj[i]);
 }
 
 for(var i = 0; i < 1024; i++) {
   obj[1] = 5;
 }
 
 for(var i = 0; i < 1024; i++) {
   assertEquals(i, obj[i]);
 }
-