Document 'W' (Rewritten) as file modification type
Document 'W' (Rewritten) as file modification type

Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>
Change-Id: I81113188e08b364b5ced6c1dcc924854f5b053d9

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