Consolidate test cases for InputMethodSubtype

We have accepted any arbitrary text as a locale
string when instantiating InputMethodSubtype object.
As a consequence, some existing code might assume
that InputMethodSubtype never canonicalize/normalize
the given locale string.

This CL add a test case for such scenario.

Change-Id: Ie08d6e149e22a60d6c4d40049a3e6afeee87dc44