Roll src/third_party/skia 6f6bef8:e975928

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/6f6bef8..e975928

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

Commits in this roll:
e975928 mtklein@chromium.org Fix -Winconsistent-missing-override in SkCodec_libgif.h

Review URL: https://codereview.chromium.org/1409603005

Cr-Commit-Position: refs/heads/master@{#354301}
1 file changed