Roll src/third_party/WebKit f5c6006:055aa2d (svn 189635:189645)

Summary of changes available at:
https://chromium.googlesource.com/chromium/blink/+log/f5c6006..055aa2d

TBR=apavlov@chromium.org,dpranke@chromium.org

Review URL: https://codereview.chromium.org/908503002

Cr-Commit-Position: refs/heads/master@{#315036}

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': 'f5c6006e764e8ee3846223d9024c634fd4c7caaf', # from svn revision 189635
+  'webkit_revision': '055aa2d0eb997928bc936cc60cf1ce52255c0328', # from svn revision 189645
   'chromium_git': 'https://chromium.googlesource.com',
   'chromiumos_git': 'https://chromium.googlesource.com/chromiumos',
   'pdfium_git': 'https://pdfium.googlesource.com',