Centralize the logic for checking public key pins from ClientSocketNSS

      and ProofVerifierChromium to TransportSecurityState::CheckPublicKeyPins.
This required adding an is_issued_by_known_root argument to this method.

In addition, CheckPublicKeyPins now only checks static pins if the
TransportSecurityState's enable_static_pins_ member is true. This defaults
to true only for official desktop builds. This also means that dynamic
pins are now checked on mobile and on non-official builds.

BUG=398925,391033

Review URL: https://codereview.chromium.org/433123003

Cr-Commit-Position: refs/heads/master@{#288435}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288435 0039d316-1c4b-4281-b951-d872f2087c98