Fixed bug with invalidation in top-level Views.

There was a bug in an InputMethod app, where popups for the keys
would not pop-down again. The problem was that they were being
marked INVISIBLE, but the new invalidation logic noop'd the
invalidate() call that used to take place. Adding to that was logic
in setFlags() that only invalidated a parent for parents that are
instanceof ViewGroup. In this case, the parent is a ViewRootImpl.

Fix is to call invalidateChild() on the parent if it's not a ViewGroup.

Change-Id: I2c2352072d383cee1367ea7ee6c2207077721fd5