Roll src/third_party/skia 6dbfb21:25b7611

Summary of changes available at:
https://chromium.googlesource.com/skia/+log/6dbfb21..25b7611

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

Review URL: https://codereview.chromium.org/878163003

Cr-Commit-Position: refs/heads/master@{#313443}

DEPS

@@ -42,7 +42,7 @@ vars = {
   'boringssl_git': 'https://boringssl.googlesource.com',
   'libvpx_revision': 'cf86fa704b0d6da24d1a9adb36001f9bc5df351f',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
-  'skia_revision': '6dbfb21a6c88af6d94e8c823c3ad559f1a41b493',
+  'skia_revision': '25b76119e949fb064c840003a2e92633c25e8cdf',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.