Roll src/third_party/skia 3d91aad:ad49b3b

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/3d91aad..ad49b3b

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

Review URL: https://codereview.chromium.org/896443002

Cr-Commit-Position: refs/heads/master@{#314162}

DEPS

@@ -42,7 +42,7 @@ vars = {
   'boringssl_git': 'https://boringssl.googlesource.com',
   'libvpx_revision': '5cdd30205301c293be6160f778bce981300b5a28',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': '3d91aad293b0f68886ed48ecfa6aa75826a27da8',
+  'skia_revision': 'ad49b3b71508aff4a371d4e487b90971d9799721',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.