As a response for bug 831460, caching of command-line switches has been introduced in CL:1010343, with different command-line switch types.

The following TODOs are remaining:
- Split the kPolicyAndFlagsAndKioskControl type to kPolicy, kFlags, kKioskControl. This should remove the need to call MaybeAppendPolicySwitches in webui flags handling.
- Consider: Do the sentinel handling for kPolicy/kFlags in user_session_manager.cc. If chrome is started with --login-user, pre-fill the flags from the command-line. This could avoid having to re-parse flags in some points.
- SetSwitchesForUser should CHECK that the passed AccountId is the primary user.