Turn off root scroller intervention on key_silk_cases page.

The http://s.codepen.io/befamous/fullpage/pFsqb?scroll pageset
seems to call preventDefault on every touchmove so to not cause
a regression with our root scroller intervention the page really
should articulate that it needs touch-action:none.

BUG=625675

Review-Url: https://codereview.chromium.org/2181413005
Cr-Commit-Position: refs/heads/master@{#408154}
1 file changed