RingtoneManager: query results depend on caller permission

When querying for ringtones, only look for ringtones on external
  storage when the caller has READ_EXTERNAL_STORAGE.
Document this behavior in the javadoc of the affected methods.

Bug 22545684

Change-Id: Iae9c9a4ccaf635da8af2ac289b6b4df1b16c5d11
1 file changed