AU: Don't send no-op operations in the delta payload.

AU: Don't send no-op operations in the delta payload.

This reduces the payload a bit and also speeds up updates on the client by
reducing the I/O.

This CL also removes a somewhat broken check for written blocks. It seems that
the intent of the check was to make sure each block is updated with some data
but since some file data blocks may be used as scratch the check is somewhat
meaningless. The CL removes the check because some blocks may never be written
if they were a part of a no-op operation.

BUG=7543
TEST=unit tests, generated a no-op delta an installed on the device

Change-Id: I31f388651a45d10dd931389a6c80ac18cb10f466

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=9fa7ec5

[petkov, 2010-10-15 18:00:43]

PTAL -- fixed bugs, added unit tests, retested

[adlr, 2010-10-18 17:32:28]

LGTM