First, he's proposed adding a new provision in Title 11, dealing with contracts generally, to add a new code section, Code Section 11-4.1:1, to void pre-waivers of payment bond claims and contract claims executed prior to providing any labor, services, or materials.
Second, he's proposed a similar pre-provision waiver of mechanic's lien rights to Code Section 43-3 that further, similarly, voids any such pre-waivers executed prior to providing any labor, services or materials.
Below is a link to the current proposed amendments of the Governor:
http://leg1.state.va.us/cgi-bin/legp504.exe?151+ful+SB891S2+pdf
Whether there is an intended distinction between the "in advance" and "prior to" language various used, as well as other interpretive aspects to the pre-waiver limitations, such as implications upon other contract payment terms, will remain to be seen if, as expected, the amendments are adopted to law.