Remove redundant arguments.

The "list" and "map" arguments of IMMS#buildInputMethodListLocked() are
nothing more than synonyms of IMMS#mMethodList and IMMS#mMethodMap,
respectively.  There is no reason to pass them as parameters.  We can
access them directly as we have done there for other member fields.

This is kind of a mechanical refactoring.  No behavior change is
intended.

Bug: 26279466
Change-Id: Ia27e19f9358ba33abbb1e5a27cebe7c9953c998f