Roll src/third_party/skia/ 6a93fa1a4..59dc54242 (2 commits).
Roll src/third_party/skia/ 6a93fa1a4..59dc54242 (2 commits).

https://chromium.googlesource.com/skia.git/+log/6a93fa1a4526..59dc5424240b

$ git log 6a93fa1a4..59dc54242 --date=short --no-merges --format='%ad %ae %s'
2016-04-05 reed remove avoid and pixelxor xfermodes
2016-04-05 borenet Whitespace change to test Bugdroid+AutoRoll

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

Review URL: https://codereview.chromium.org/1860953002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#385171}

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