Don't install private script class without a context document

In HTMLMarqueeElement's constructor, don't try to install the private
script class if there is no context document. Doing so is doesn't work,
and will crash (safely).

BUG=456624

Review URL: https://codereview.chromium.org/918433004

git-svn-id: svn://svn.chromium.org/blink/trunk@189958 bbb929c8-8fbe-4397-9dbb-9b2b20218538
1 file changed
tree: 86b18bbeb2a453f2420a98dc99cad1ccfc25865e
  1. third_party/