Compile File Manager Private API on Chrome OS only.
Compile File Manager Private API on Chrome OS only.

This API is used on Chrome OS only. No need to compile the schema on all
operating systems.

TEST=All current Files app tests pass.
BUG=None

Review URL: https://codereview.chromium.org/1093923006

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#326821}

Fireblend/chromium-crosswalk,Fireblend/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,Just-D/chromium-1,chuan9/chromium-crosswalk,Just-D/chromium-1,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Fireblend/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,chuan9/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,chuan9/chromium-crosswalk,Chilledheart/chromium,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,Chilledheart/chromium,TheTypoMaster/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,Pluto-tv/chromium-crosswalk,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,axinging/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,Chilledheart/chromium,Just-D/chromium-1,Just-D/chromium-1