samples/pop_pop_win: now based on StageXL
samples/pop_pop_win: now based on StageXL

R=sigmund@google.com

Review URL: https://codereview.chromium.org//242443008

Patch from K. Alex Gann <k.alexgann@gmail.com>.

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@35231 260f80e4-7a28-3924-810f-c04153c831b5

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