GitLab

When the Security.showCertificateViewer command is received by the
browser, it should show the certificate for the visible entry, not
necessarily the last committed entry, because there might be a transient
entry for an interstitial overlaying the last committed entry.

BUG=647759

Review-Url: https://codereview.chromium.org/2344113003
Cr-Commit-Position: refs/heads/master@{#419359}