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

test/mjsunit/regress/regress-998565.js

 // Copyright 2008 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 30 matching lines @@
 
 function f() {
  a=1
 };
 
 // Set a break point and call to invoke the debug event listener.
 Debug.setBreakPoint(f, 0, 0);
 f();
 
 // Make sure that the debug event listener vas invoked.
-assertTrue(listenerCalled);
+assertTrue(listenerCalled);