Roll src/third_party/skia/ de3a726ad..50b98b424 (4 commits).
Roll src/third_party/skia/ de3a726ad..50b98b424 (4 commits).

https://chromium.googlesource.com/skia.git/+log/de3a726ad38b..50b98b424ccf

$ git log de3a726ad..50b98b424 --date=short --no-merges --format='%ad %ae %s'
2016-02-03 reed add note about security and new subclasses
2016-02-03 benjaminwagner Revert of Work around exasperating Google3 Android build error. (patchset #1 id:1 of https://codereview.chromium.org/1649493005/ )
2016-02-03 msarett Fix Unpremul Index8 tests
2016-02-03 msarett SSE optimizations for GrayAlpha -> RGBA/BGRA Premul/Unpremul

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

Review URL: https://codereview.chromium.org/1668713002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#373456}

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