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

test/webkit/fast/regex/assertion.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 89 matching lines @@
 shouldBe("regex21.exec('aab')", "['aab']");
 
 var regex22 = /(?!(u|m{0,}g+)u{1,}|2{2,}!1%n|(?!K|(?=y)|(?=ip))+?)(?=(?=(((?:7))*?)*?))p/m;
 shouldBe("regex22.exec('55up')", "null");
 
 var regex23 = /(?=(a)b|c?)()*d/;
 shouldBe("regex23.exec('ax')", "null");
 
 var regex24 = /(?=a|b?)c/;
 shouldBe("regex24.exec('x')", "null");
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