leanback: Fix ItemDecoration

1. We should skip the optimizaton of checking isLayoutRequested()
   Because when child view's decoration changes,  it will not
   be layout requested.
2. calculate opticalInsets is wrong, it doesn't count the decoration
   offset, so incorrectly put decoration insets as optical insets.

Bug 27794028

Change-Id: Ide4f907764a4f35507c32ba3db764f8ad4ccd090
3 files changed