Roll src/third_party/skia/ 113628d76..20f00784b (5 commits).

https://skia.googlesource.com/skia.git/+log/113628d76176..20f00784b850

$ git log 113628d76..20f00784b --date=short --no-merges --format='%ad %ae %s'
2017-02-02 mtklein Restore ios_flavor.
2017-02-03 bsalomon Make shadow tessellators fail gracefully and add unit test for this.
2017-02-03 senorblanco GrTessellator (AA): Fix for missing fill artifacts.
2017-02-03 jvanverth Initialize some more variables in SpotShadowTessellator
2017-02-02 reed experimental tight-bounds

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
TBR=halcanary@google.com

Review-Url: https://codereview.chromium.org/2674573009
Cr-Commit-Position: refs/heads/master@{#448028}

DEPS

@@ -40,7 +40,7 @@ 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': '113628d76176a1ab3e6719c59efff23cd10ab213',
+  'skia_revision': '20f00784b8500ccb68f0e402eeccd9bbf2707040',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.