Start deprecation of PacHttpsUrlStrippingEnabled policy

This change removes enterprise_default for PacHttpsUrlStrippingEnabled,
that was set to "False" and now all users should have it set to "True".
Long-term security-wise the behavior should be that URLs are always
stripped for Pac proxies, i.e.as the policy set to "True".

We are keeping ability to change the policy in server-side configuration
to "False" in case customers will be broken by the change.

Otherwise, the policy is going to be deprecated in M74.

Bug: 619087
Change-Id: I29db0211ced988b0fde5efaf3ce7863466bffb6e
Reviewed-on: https://chromium-review.googlesource.com/1224449
Commit-Queue: Sergey Poromov <poromov@chromium.org>
Reviewed-by: Eric Roman <eroman@chromium.org>
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591330}
1 file changed