We've decided that controlling scroll blocking behavior is something that really needs to be tied to event listeners via a JS API, not a CSS property. The platform needs to mediate the composition here (eg. for two unrelated libraries both adding touch handlers to the document), and there's no good way to mediate that composition using CSS. It's really a property of the event handler and so should be specified at addEventListener time. http://crbug.com/489802 tracks the first step of that design (EventListenerOptions). So it's time to remove the scroll-blocks-on CSS support from blink. I expect the utlimate compositor integration for EventListenerOptions mayCancel to be similar, and so for now I'm leaving the hooks in place in GraphicsLayer. This change also fixes a regression where iframes could occasionally not get displayed. I don't understand how the scroll-blocks-on code (even when not enabled) was triggering that problem, but since it's going away I'm not going to investigate further. BUG=347272, 490358 Review URL: https://codereview.chromium.org/1287623002 git-svn-id: svn://svn.chromium.org/blink/trunk@200448 bbb929c8-8fbe-4397-9dbb-9b2b20218538