Roll src/third_party/skia/ 6e9a4f632..8b858526f (5 commits)

https://skia.googlesource.com/skia.git/+log/6e9a4f6327d1..8b858526faf4

$ git log 6e9a4f632..8b858526f --date=short --no-merges --format='%ad %ae %s'
2018-03-16 angle-skia-autoroll Roll skia/third_party/externals/angle2/ 5ae6ee457..1c08cbb39 (1 commit)
2018-03-16 reed fix nextContour bug
2018-03-16 egdaniel Fix Vulkan Copy as draw shader
2018-03-16 robertphillips Prevent crash when flushing while DDL recording
2018-03-15 brianosman Support GL_OES_EGL_image_external on newer GLSL without essl3

Created with:
  roll-dep src/third_party/skia


The AutoRoll server is located here: https://autoroll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel;luci.chromium.try:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
TBR=stephana@chromium.org

Change-Id: I483b6a2403c5cef903b5bed56d30fdea2988c21e
Reviewed-on: https://chromium-review.googlesource.com/966586
Commit-Queue: skia-chromium-autoroll <skia-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Reviewed-by: skia-chromium-autoroll <skia-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#543744}

DEPS

@@ -79,7 +79,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and whatever else without interference from each other.
-  'skia_revision': '6e9a4f6327d1c9b1cac26d4d091b9f4fbb0cf4fc',
+  'skia_revision': '8b858526faf4990484f8b14cad4e84ad655125d5',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.