Fix DiffFormatter for diffs against working tree with autocrlf=true

Fix DiffFormatter for diffs against working tree with autocrlf=true

The WorkingTreeSource produced an ObjectLoader that returned
inconsistent sizes: the file size in getSize(), but then a
correctly filtered smaller stream in openStream(). This resulted
either in an IOE "short read of block" or in an EOFException
depending on the resulting filtered size.

Fix this by ensuring that getSize() does return the size of the
filtered stream.

Bug: 530106
Change-Id: I7c7c85036047dc10030ed29c1d5a6c7f34f2bdff
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>