Roll src/third_party/skia/ 70509762c..3819d2d76 (8 commits).
Roll src/third_party/skia/ 70509762c..3819d2d76 (8 commits).

https://chromium.googlesource.com/skia.git/+log/70509762c88d..3819d2d767a1

$ git log 70509762c..3819d2d76 --date=short --no-merges --format='%ad %ae %s'
2015-12-17 ethannicholas Added concave paths to aaxfermodes GM GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1534823004
2015-12-17 mtklein update CMake and Google3 builds for AVX/AVX2
2015-12-17 bsalomon Move the GrGLGpu config stencil format index into ConfigTable GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1526253007
2015-12-17 rmistry Add 2 new SKPS to the buildbot repository
2015-12-17 jvanverth Don't allow BGRA rendertargets on iOS w/ES 3.0+.
2015-12-17 fs Use the unswapped end point y for early out case in winding_line
2015-12-17 bsalomon Fix thread-unsafe construction of GrUniqueKey in GR_DEFINE_STATIC_UNIQUE_KEY GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1530313002
2015-12-17 senorblanco Fix gaussian blur for small sigma.

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

Review URL: https://codereview.chromium.org/1532153002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#365898}

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