Move atomicinc in GrTracing to behind branch

TBR=bsalomon@google.com
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1571603003

Review URL: https://codereview.chromium.org/1571603003
3 files changed