The interface that plural rules must implement. Implementations of
this interface will be used both at compile time (pluralForms) and
at run time (select), so implementations must be both translatable
and not reference JSNI methods.
Returns the list of values which are valid for this rule. The
default or "other" plural form must be first in the list with
an index of 0 -- this form will be used if no other form applies
and is also mapped to the default text for a given message.
This method will be executed at compile time and may not contain
any references, even indirectly, to JSNI methods.
int select(int n)
Returns the plural form appropriate for this count.
This method will be executed at runtime, so must be translatable.
n - count of items to choose plural form for
the plural form to use (must be a valid index
into the array returned by pluralForms).