Blink roll 31d45bf:2504b5a

https://chromium.googlesource.com/chromium/blink/+log/31d45bf6e4c602a8f3e231037bb4c7fe6865e614..2504b5ab42fcfdb91c782eabef1b1118b61d8749
TBR=hclam@chromium.org,tkent@chromium.org

Review URL: https://codereview.chromium.org/528873002

Cr-Commit-Position: refs/heads/master@{#292894}

DEPS

@@ -28,7 +28,7 @@ vars = {
   'libcxxabi_revision': '062ba40d41870a04e0aefb64f8122e91aa824147',
   'webkit_trunk': 'http://src.chromium.org/blink/trunk',
   'nacl_trunk': 'http://src.chromium.org/native_client/trunk',
-  'webkit_revision': '31d45bf6e4c602a8f3e231037bb4c7fe6865e614', # from svn revision 181200
+  'webkit_revision': '2504b5ab42fcfdb91c782eabef1b1118b61d8749', # from svn revision 181202
   'chromium_git': 'https://chromium.googlesource.com',
   'chromiumos_git': 'https://chromium.googlesource.com/chromiumos',
   'pdfium_git': 'https://pdfium.googlesource.com',