Process: Fix communication with zygote.

Don't write partial requests, and don't return (or throw) early after
partially reading a response.

bug: 30143607

(cherry picked from commit 448be0a62209c977593d81617853a8a428d013df)

Change-Id: Ib283b1620947151338f5f9473891a048a17d8f4a
1 file changed