Use the Document rather than the Frame's execution context to install JS-based marquee elements

Depending on the frame results in a crash inside <template> tags, which don't have one.

BUG=421002

Review URL: https://codereview.chromium.org/654583003

git-svn-id: svn://svn.chromium.org/blink/trunk@184229 bbb929c8-8fbe-4397-9dbb-9b2b20218538