Set Token-Binding HTTP header

Adds a new method to SSLClientSocket to get the Token Binding from an SSL
connection where Token Binding was negotiated, and uses that to add the
Set-Token-Binding HTTP header (only when Token Binding was negotiated).

BUG=467312

Review URL: https://codereview.chromium.org/1378613004

Cr-Commit-Position: refs/heads/master@{#371347}
55 files changed