The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/51a75fa55ba71462963ddcf085995cf3eca66104

commit 51a75fa55ba71462963ddcf085995cf3eca66104
Author: fs <fs@opera.com>
Date: Wed Dec 07 17:45:36 2016

Don't check 'visibility' in LayoutSVGResourceMasker

Since 'visibility' does not work in the same way as 'display', it's not
possible to "prune" subtrees based on non-'visible' values of the
property. Remove the check from the two methods that use it, and leave
to lower levels to handle it.

BUG= 672055 

Review-Url: https://codereview.chromium.org/2558793002
Cr-Commit-Position: refs/heads/master@{#436996}

[add] https://crrev.com/51a75fa55ba71462963ddcf085995cf3eca66104/third_party/WebKit/LayoutTests/svg/masking/mask-with-visibility-hidden-group-expected.html
[add] https://crrev.com/51a75fa55ba71462963ddcf085995cf3eca66104/third_party/WebKit/LayoutTests/svg/masking/mask-with-visibility-hidden-group.html
[modify] https://crrev.com/51a75fa55ba71462963ddcf085995cf3eca66104/third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceMasker.cpp