Roll src/third_party/skia 953df44:6bc1b5f

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/953df44..6bc1b5f

CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel,linux_blink_dbg
TBR=reed@google.com

Review URL: https://codereview.chromium.org/942113003

Cr-Commit-Position: refs/heads/master@{#317615}

DEPS

@@ -42,7 +42,7 @@ vars = {
   'boringssl_git': 'https://boringssl.googlesource.com',
   'libvpx_revision': '33bbffe8b3fa6d240ab7720f4f46854bd98d7198',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': '953df445aba3e657ab3a3b0da8041ff0a7e72b5f',
+  'skia_revision': '6bc1b5fab8554a9cb643277b4867965dd4535cd6',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.