Roll src/third_party/skia cd87c51:f421ec6

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/cd87c51..f421ec6

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

Review URL: https://codereview.chromium.org/943583002

Cr-Commit-Position: refs/heads/master@{#317052}

DEPS

@@ -42,7 +42,7 @@ vars = {
   'boringssl_git': 'https://boringssl.googlesource.com',
   'libvpx_revision': '5cdd30205301c293be6160f778bce981300b5a28',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': 'cd87c51de6bf81ed232b5d828c88771829c0bf76',
+  'skia_revision': 'f421ec6cc9c8f32d717b9b1df71fd9e79817a16c',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.