Roll src/third_party/skia/ 64593525d..c94cd7cc0 (2 commits).
Roll src/third_party/skia/ 64593525d..c94cd7cc0 (2 commits).

https://chromium.googlesource.com/skia.git/+log/64593525debc..c94cd7cc01b6

$ git log 64593525d..c94cd7cc0 --date=short --no-merges --format='%ad %ae %s'
2015-11-12 cdalton Fix GrCoverageSetOpXP unit test on mixed samples
2015-11-12 mtklein SkAtomic: always use std::atomic

CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
TBR=borenet@google.com

Review URL: https://codereview.chromium.org/1442753003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#359425}

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