Simplify code flow for add starting window.

Remove unnecessary code, no logic change.
Also remove testTransferStartingWindowWhileCreating, it is impossible
to have such code path since there won't create starting window inside
core anymore.

Bug: 341054451
Test: presubmit
Change-Id: I3a27952160bc26bd9618ce96e5c692c78d0983b2
6 files changed