Roll src/third_party/skia 0acf1b4:b1c6843

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/0acf1b4..b1c6843

CQ_EXTRA_TRYBOTS=tryserver.blink:linux_blink_rel,linux_blink_dbg
TBR=bungeman@google.com

Review URL: https://codereview.chromium.org/822873002

Cr-Commit-Position: refs/heads/master@{#309533}

DEPS

@@ -44,7 +44,7 @@ vars = {
   'boringssl_git': 'https://boringssl.googlesource.com',
   'libvpx_revision': 'd3f3dcefb055656807e8a2f65a322bbb13cd05a4',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': '0acf1b4b3645772d220c720313821bac389751b5',
+  'skia_revision': 'b1c6843af963fc5bdcf5031f7d58b54aa5e9822b',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.