Roll src/third_party/WebKit 1175397:ef73ddc (svn 190862:190879)

Summary of changes available at:
https://chromium.googlesource.com/chromium/blink/+log/1175397..ef73ddc

TBR=arv@chromium.org,timvolodine@chromium.org

Review URL: https://codereview.chromium.org/960013003

Cr-Commit-Position: refs/heads/master@{#318181}

DEPS

@@ -34,7 +34,7 @@ vars = {
   'llvm_url': 'http://src.chromium.org/llvm-project',
   'llvm_git': 'https://llvm.googlesource.com',
   'webkit_trunk': 'http://src.chromium.org/blink/trunk',
-  'webkit_revision': '11753971ee1d364150e2aefa2ebeeaea475296e4', # from svn revision 190862
+  'webkit_revision': 'ef73ddce61bdd8de9ac6d50aaaf5332172753dfb', # from svn revision 190879
   'chromium_git': 'https://chromium.googlesource.com',
   'chromiumos_git': 'https://chromium.googlesource.com/chromiumos',
   'pdfium_git': 'https://pdfium.googlesource.com',