Roll src/third_party/skia 6bd4196:3b8af07

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/6bd4196..3b8af07

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

Review URL: https://codereview.chromium.org/614103008

Cr-Commit-Position: refs/heads/master@{#297884}

DEPS

@@ -35,7 +35,7 @@ vars = {
   'boringssl_git': 'https://boringssl.googlesource.com',
   'libvpx_revision': 'efe9712d52c2d216fb3d1ceb508b8148847a7e4b',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': '6bd41969a0f2283a7a7320bb0025551353c241ec',
+  'skia_revision': '3b8af078281a5a20f951b9fd84f38d92b8f6217b',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.