Avoid mapping output to memory while writing to a file.

It's unnecessary, and causes issues when the uncompressed
output is large.

Bug: http://b/21558406
Change-Id: I99cfb3933b094c2826c7e6c6de9aab03478fcc53
(cherry picked from commit f899bd534b2dc51b9db8d27c76394b192fe51155)
2 files changed