https://codereview.chromium.org/2709523008/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/308019e846c5f06e679550aadd002b888a9690a0

commit 308019e846c5f06e679550aadd002b888a9690a0
Author: ryanchung <ryanchung@chromium.org>
Date: Tue Mar 21 03:19:50 2017

[Cast Channel] Add support for nonce challenge to Cast channel authentication.

Include feature flag and histograms.
A nonce challenge is sent to the Cast receiver. The challenge is expected
to be included in the signature supplied in the authentication response.

BUG= 694868 

Review-Url: https://codereview.chromium.org/2709523008
Cr-Commit-Position: refs/heads/master@{#458292}

[add] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/components/test/data/cast_certificate/certificates/test_tls_cert.pem
[modify] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/extensions/browser/api/cast_channel/cast_auth_util.cc
[modify] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/extensions/browser/api/cast_channel/cast_auth_util.h
[modify] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/extensions/browser/api/cast_channel/cast_auth_util_unittest.cc
[modify] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/extensions/browser/api/cast_channel/cast_message_util.cc
[modify] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/extensions/browser/api/cast_channel/cast_message_util.h
[modify] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/extensions/browser/api/cast_channel/cast_socket.cc
[modify] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/extensions/browser/api/cast_channel/cast_socket.h
[modify] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/extensions/browser/api/cast_channel/cast_socket_unittest.cc
[modify] https://crrev.com/308019e846c5f06e679550aadd002b888a9690a0/tools/metrics/histograms/histograms.xml