fix file data align to 4
Change-Id: Ie88c46521e216b3f83a8dc3495591cd19bce83c6
GitHub-Last-Rev: aebf3cd7ff0d77050659e9269f7eddaeff364eff
GitHub-Pull-Request: golang/mobile#73
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/351789
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Hajime Hoshi <hajimehoshi@gmail.com>
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>