Include InputMethodSubtypeSwitchingController in state dump.

In order to diagnose IME issues in multi-user / multi-profile
environment, internal state of
InputMethodSubtypeSwitchingController needs to be included in
the bugreport.

Bug: 19340792
Bug: 19587437
Bug: 21612582
Change-Id: I34aca2c1a4330ec08b5e40441e631809a8bb844e