Skia roll 6d13420:7843a24

https://skia.googlesource.com/skia/+log/6d134201a90692b0c7a1c0c4a97c894dae7b2158..7843a24ab2c2dc4fe77e82b9689cde953d6abd7c

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

Review URL: https://codereview.chromium.org/521143003

Cr-Commit-Position: refs/heads/master@{#292796}

DEPS

@@ -38,7 +38,7 @@ vars = {
   # to update other nacl_*_revision's.
   'libvpx_revision': '982d14793a8e42d2fa5e6e5e34bede17b4ba67e3', # r291730
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': '6d134201a90692b0c7a1c0c4a97c894dae7b2158',
+  'skia_revision': '7843a24ab2c2dc4fe77e82b9689cde953d6abd7c',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.