Only delay scrolling for FrameViews

Widgets that are implemented with ScrollViews may not
scroll properly since the delayed scroll is implemented
in FrameView. This should fix the issue.

BUG=357480

Review URL: https://codereview.chromium.org/223083003

git-svn-id: svn://svn.chromium.org/blink/trunk@170825 bbb929c8-8fbe-4397-9dbb-9b2b20218538