Track TextView locale changes if not explicitly set

The locale in the Paint used by TextView is set at the time the view
is created. If the locale changes and the locale hasn't been explicitly
set, better behavior is "whatever the current locale is." This patch
updates the locale in that particular case.

Bug: 16274782
Change-Id: I3b1b8e77c9508c757543ea50de3590d254404c1e