Roll src/third_party/WebKit 481d9a8:6998a13 (svn 183830:183832)

Summary of changes available at:
https://chromium.googlesource.com/chromium/blink/+log/481d9a8..6998a13

TBR=cbiesinger@chromium.org,dstockwell@chromium.org

Review URL: https://codereview.chromium.org/641223003

Cr-Commit-Position: refs/heads/master@{#300005}

DEPS

@@ -36,7 +36,7 @@ vars = {
   'libcxx_revision': '48198f9110397fff47fe7c37cbfa296be7d44d3d',
   'libcxxabi_revision': '4ad1009ab3a59fa7a6896d74d5e4de5885697f95',
   'webkit_trunk': 'http://src.chromium.org/blink/trunk',
-  'webkit_revision': '481d9a85a72733784a9e50ad0507ad6cc69d6bcf', # from svn revision 183830
+  'webkit_revision': '6998a13dd2d5d755003060bfac419681a6a67300', # from svn revision 183832
   'chromium_git': 'https://chromium.googlesource.com',
   'chromiumos_git': 'https://chromium.googlesource.com/chromiumos',
   'pdfium_git': 'https://pdfium.googlesource.com',