Create window decors for leaf tasks & skip non-leafs

Fixes the logic that intended to filter out window decorations for
non-leaf tasks. Previously, non-root leafs were mistakenly skipped
instead of their parents, which went unnoticed until freeform tasks
were nested and the non-root leafs were missing the caption bar.

Bug: None
Test: nest freeform tasks, leaf tasks have window decorations.
Change-Id: Ia958fb43319d17a0e33e28497e52293954706416