Add initial CC support for scroll-blocks-on
When 'scroll-blocks-on: scroll-event' is applied anywhere in the scroll ancestor tree where is a scroll event handler, force the scroll to be executed on the main thread. Note that this is still experimental. We'll be at least adding a timeout mechanism to this to mitigate the risk of improper usage.
When 'scroll-blocks-on: wheel-event' is NOT applied (it's on by default), ignore the existence of wheel event handlers (allowing scrolling to run freely on impl).
When 'scroll-blocks-on: start-touch' is NOT applied (it's on by default), suppress sending touch events to blink. Eventually we'll make this smarter - sending async touch events that don't block scroll.
Depends on blink change https://src.chromium.org/viewvc/blink?view=rev&revision=188230
BUG=347272
Review URL: https://codereview.chromium.org/784463002
Cr-Commit-Position: refs/heads/master@{#314765}
16 files changed
