add multipart build opt

Change-Id: Ie2d6db01e537bd5baf587d1a232ab003afe7deab
Disable audiosync

Change-Id: I3fa41aeda218e999f6a683db2f87204c11974593
use closure() to wrap closures

Change-Id: Ib763705d937dcf67051a40316c98e4f25c6668c1
http_v2 can parse filename

Change-Id: I29a50d0a758166df3938a445e1766d1b55dc1ae9
http_v2: if no filename, filename is nil

Change-Id: Ib9e198746ce7b5ede9ec332f8dd72c97c2f3c3a0