Roll src/third_party/skia/ 15bb26ec7..25954b64c (8 commits)

https://skia.googlesource.com/skia.git/+log/15bb26ec70c9..25954b64c066

$ git log 15bb26ec7..25954b64c --date=short --no-merges --format='%ad %ae %s'
2017-08-15 mtklein explicitly vectorize sk_memset{16,32,64}
2017-08-15 mtklein upstream cr/165303354
2017-08-15 herb Fix bogus math in object allocation.
2017-08-15 fmalita Revert "Fix bogus math in object allocation."
2017-08-15 bungeman Remove SkTypeface::style().
2017-08-15 herb Fix bogus math in object allocation.
2017-08-15 fmalita Skip bilerp for integral-translate-only matrices (!clamp-clamp case)
2017-08-15 brianosman Speed up convexpaths GM in debug builds

Created with:
  roll-dep src/third_party/skia
BUG=755391,744109,744109,744674


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

If the roll is causing failures, see:
http://www.chromium.org/developers/tree-sheriffs/sheriff-details-chromium#TOC-Failures-due-to-DEPS-rolls


CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel
TBR=bsalomon@chromium.org

Change-Id: I14e7599bb7b37734099f0984baf5e6488e5b3e10
Reviewed-on: https://chromium-review.googlesource.com/616164
Reviewed-by: Skia Deps Roller <skia-deps-roller@chromium.org>
Commit-Queue: Skia Deps Roller <skia-deps-roller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#494622}