Allow running versions of optipng which require the input filename last.
Allow running versions of optipng which require the input filename last.

At least the version of optipng I run on my Windows box requires all
command-line flags to come before the input filename.

BUG=none
TEST=none
TBR=oshima

Review URL: https://codereview.chromium.org/1371833004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#352470}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk