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

test/mjsunit/debug-liveedit-compile-error.js

 // Copyright 2012 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 38 matching lines @@
       orig_animal.length, new_animal_patch, change_log);
 } catch (e) {
   caught_exception = e;
 }
 
 assertNotNull(caught_exception);
 assertEquals("Unexpected token )",
     caught_exception.details.syntaxErrorMessage);
 
 assertEquals(2, caught_exception.details.position.start.line);
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