Roll src/third_party/skia 11ed6b8:976386b

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/11ed6b8..976386b

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

Review URL: https://codereview.chromium.org/674043002

Cr-Commit-Position: refs/heads/master@{#301036}

DEPS

@@ -44,7 +44,7 @@ vars = {
   'boringssl_git': 'https://boringssl.googlesource.com',
   'libvpx_revision': 'efe9712d52c2d216fb3d1ceb508b8148847a7e4b',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': '11ed6b8140ad067bf64087b5b0deca8fe903d20c',
+  'skia_revision': '976386b75d883eebaa4d2f19c4ae0222f3f85c0a',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.