Fix cold-start non-flush
Fix cold-start non-flush

Summary: Flush the last dex if it did not fill up.

Reviewed By: jimmycFB

Differential Revision: D34907582

fbshipit-source-id: 65d0cd5f13a14e7a32fbd53cbc3f72c09a364278

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex