At a high level, Chrome uses the CertVerifier interface (async) for certificate verification, but all the platform-specific implementations are connected through CertVerifierProc (sync).
This poses a complication in that the new path building code is asynchronous, so a drop-in CertVerifierProc (sync) for it is not appropriate.
The obvious integration point then would be to create a new CertVerifier for the new path builder, and forego MultiThreadedCertVerifier. That will mean hoisting out the logic that currently lives in CertVerifierProc which should be common to both, such as:
* Certificate blacklists/whitelists (i.e. CNNIC)
* Histograms around key sizes
* Baseline requirement restrictions on validity times
* Checking weak keys in chain
Comment 1 by eroman@chromium.org
, Sep 21 2016