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

test/webkit/dfg-add-not-number.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 // 1.  Redistributions of source code must retain the above copyright
 //     notice, this list of conditions and the following disclaimer.
 // 2.  Redistributions in binary form must reproduce the above copyright
 //     notice, this list of conditions and the following disclaimer in the
@@ skipping 14 matching lines @@
 "Tests that adding things that aren't numbers using ++ does not crash or generate bogus code."
 );
 
 function foo(a) {
     a++;
     return a;
 }
 
 for (var i = 0; i < 100; ++i)
     shouldBe("foo(\"foo\" + i)", "NaN");
-