Each default preference needs to have its corresponding
PreferenceAvailabilityProvider to provide us the availability of it.
If no corresponding provider is found, it is considered to be not
available. So it encourages other developers who will add new default app
preference later to consider the availability of it.
Bug:27143673
Change-Id: I073b7122dddc579504f397c5de2bdd4df3826269
1. Print settings already support managed profile. Follow the UI of that.
ProfileSettingsPreferenceFragment is created to act as the base class
for per-profile setting.
2. Only show browser and dialer default setting in managed profile.
BUG=26707733
Change-Id: I20d00203e14db58ec03638f692dd83a1bd50c59c