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

test/mjsunit/regress/regress-crbug-233737.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 21 matching lines @@
 assertTrue(%HasFastSmiElements(a));
 assertTrue(%HasFastHoleyElements(a));
 
 function hole(i) {
   return a[i] << 0;
 }
 
 assertEquals(1, hole(0));
 assertEquals(1, hole(0));
 %OptimizeFunctionOnNextCall(hole);
-assertEquals(0, hole(1));
+assertEquals(0, hole(1));