1. Create log item as LLD rule

log[/tmp/test.log,,,1]

2. file contents are

{"data":[{"{#FOO}":"dummy", "{#VALUE}":"0"}]}
{"data":[{"{#FOO}":"dummy2", "{#VALUE}":"2"}]}

3. Start server and then agent.
Observe:
select mtime,lastlogsize from items where name like 'log%';
See lastlogsize is changed, now clone host and see that lastlogsize is cloned to new item.

Alternatively create active item, LLD rule, item prototype with log key and manually enter values into DB field "lastlogsize" and "mtime". Clone host and observe fields being copied.

As for older versions like 4.0 this applies only to LLD rules, so decided to fix only in 4.2

(MOVED from ZBXNEXT-4854)