'I, Ji Chen, hereby sign-off-by all past commits to this repo subject to the Developer Certificate of Origin (DCO), Version 1.1.'
'I, Huang Rui, hereby sign-off-by all past commits to this repo subject to the Developer Certificate of Origin (DCO), Version 1.1.'

Add sign off doc for old code
Add sign off doc for old code

Change-Id: If30aed99a9a903d247a61e418c45b80b5e8ef49a
