Roll src/third_party/skia a392c9d:a29b5d8

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/a392c9d..a29b5d8

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

Review URL: https://codereview.chromium.org/590123003

Cr-Commit-Position: refs/heads/master@{#295969}

DEPS

@@ -35,7 +35,7 @@ vars = {
   'boringssl_git': 'https://boringssl.googlesource.com',
   'libvpx_revision': '42ddeba4a7ad6382898ef2e57dc4bd9f9da57aca',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': 'a392c9d423abb4db99d8398e7c2365a4ced5ce56',
+  'skia_revision': 'a29b5d8430ada72bc73b1e6e1b8f09e4b046b2ff',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.