[Cast channel] Add feature to allow Cast devices on all IPs.

This is a workaround for enterprise setups (such as universities) where
the network topology assigns public IP addresses to their Cast devices
(presumably these devices are protected behind a firewall). Public IP
addresses were disallowed in crrev.com/519857 which causes such setup
to be broken, as users can no longer connect to those devices. To our
knowledge there are at least 2 EDU setups (and a handful of individual
users) that were affected by this.

The workaround is implemented as a feature that is disabled by default.
The intended target is affected users for whom the option of changing
the Cast devices is infeasible (mostly EDU organizations). It can be
enabled by passing in --enable-features=CastAllowAllIPs in the
command line, or by turning it on in chrome://flags.

Bug: 813974
Change-Id: Ia02702315f02544245862561dc6925f0e15725db
Reviewed-on: https://chromium-review.googlesource.com/954345
Reviewed-by: mark a. foltz <[email protected]>
Commit-Queue: Derek Cheng <[email protected]>
Cr-Commit-Position: refs/heads/master@{#542557}
8 files changed