From browser.js's point of view there's no difference between restricted and guest profiles. Both use the
parental controls API. So there are only two "simple" solutions here:
* 1) Add a method to nsIParentalControlsService to determine whether the current profiles is a restricted or
a guest profile (Something like isGuest()). But then every platform using this interface would require
to at least implement a stub for this method.
* 2) Add a new restriction that controls installing the theme.
This patch implements option 2. While this restriction is not of much use besides deciding whether we need
to install a specialized theme (DISALLOW_DEFAULT_THEME), it still offers the most flexibility. In a
follow-up bug we could decide to make the restriction configurable by the device admin (requires localized
strings).
* Synchronize nsIParentalControlsService.idl and Restriction.java
* Do not hide 'tools' menu but menu items of disabled features
* Hiding 'Report site issue' should not be configurable
* Restricted profiles: DISALLOW_INSTALL_APPS is a system restriction and should not be configurable
* RestrictedProfileConfiguration: Use AboutPages
