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

test/mjsunit/regress/regress-105.js

 // Copyright 2013 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 23 matching lines @@
   assertEquals(String, custom_toString.caller);
   return "I used to be an adventurer like you";
 }
 
 var object = {};
 object.valueOf = custom_valueOf;
 object.toString = custom_toString;
 
 assertEquals(2, Number(object));
 assertEquals('I', String(object)[0]);
-