WKWebView: Do not DCHECK on invalid CertVerifierBlockAdapter::Params.
cert and hostname params are coming from System API and both can
potentially be null. For CertVerifierBlockAdapter client
(web controller) it will be more convenient not to handle a special case
with invalid cert and/or hostname. Instead params error will be handled
in completionHandler block along with other errors.
BUG=462427
Review URL: https://codereview.chromium.org/
1231783003
Cr-Commit-Position: refs/heads/master@{#338517}