Roll src/third_party/skia 5245cb4:50785a3

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/5245cb4..50785a3

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

Review URL: https://codereview.chromium.org/872893005

Cr-Commit-Position: refs/heads/master@{#315045}

DEPS

@@ -42,7 +42,7 @@ vars = {
   'boringssl_git': 'https://boringssl.googlesource.com',
   'libvpx_revision': '5cdd30205301c293be6160f778bce981300b5a28',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': '5245cb427f982dbae365a52cf19256cfbcc6870a',
+  'skia_revision': '50785a3d10b53bea5beb6e18431a2449860be237',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.