Update BUILD.gn and properly disable it on android
Update BUILD.gn and properly disable it on android

BUG=none
R=dcarney@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/294613002

git-svn-id: f98b9d40cb02301bc76fa9e1b46ee668158567fd@21361 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh