WIP: NSS trust store integration for path builder.

WIP: NSS trust store integration for path builder.

* Changes TrustStore interface to allow async results.
* Makes TrustStore be a CertIssuerSource instead of having its own custom way to retrieve the certs.
* Introduces CertIssuerSourceCollection class to combine multiple CertIssuerSources instead of doing that inline in path builder. (May want to split this into separate CL.)
* Similar for TrustStoreCollection.

BUG=410574

[mattm, 2016-07-07 01:56:48]

Description was changed from

==========
WIP: NSS trust store integration for path builder.

* Changes TrustStore interface to allow async results.
* Makes TrustStore be a CertIssuerSource instead of having its own custom way to
retrieve the certs.
* Introduces CertIssuerSourceCollection class to combine multiple
CertIssuerSources instead of doing that inline in path builder.
* Similar for TrustStoreCollection.

BUG=410574
==========

to

==========
WIP: NSS trust store integration for path builder.

* Changes TrustStore interface to allow async results.
* Makes TrustStore be a CertIssuerSource instead of having its own custom way to
retrieve the certs.
* Introduces CertIssuerSourceCollection class to combine multiple
CertIssuerSources instead of doing that inline in path builder. (May want to
split this into separate CL.)
* Similar for TrustStoreCollection.

BUG=410574
==========

[mattm, 2016-07-07 01:56:48]

mattm@chromium.org changed reviewers:
+ eroman@chromium.org

[mattm, 2016-07-07 02:00:13]

Just sending this as an FYI so you can see what I have in flight. You could do a
high-level review of the design & interfaces if you want.