Remove blink::network_utils::IsOriginSecure

After [1], blink::network_utils::IsOriginSecure is strictly equivalent
to network::IsUrlPotentiallyTrustworthy. This CL removes IsOriginSecure,
performs corresponding replacements and optionally adjusts DEPS files.
Some conditions webauth_request_security_checker.cc and
mixed_content_navigation_throttle.cc are also simplified, because
checks are already included in network::IsUrlPotentiallyTrustworthy.
There is no behavior changes, although uses of IsOrigin vs IsUrl may
need to be reviewed in follow-up CLs [2].

[1] https://chromium-review.googlesource.com/c/chromium/src/+/2563683/1
[2] https://bugs.chromium.org/p/chromium/issues/detail?id=1158302

Bug: 1153336
Change-Id: Ibd1828c14d92c33291095174dbeb466259cc4530
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2563883
Reviewed-by: Cait Phillips <[email protected]>
Reviewed-by: Avi Drissman <[email protected]>
Reviewed-by: Matt Falkenhagen <[email protected]>
Commit-Queue: Frédéric Wang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#837622}