Purge the ScrollBlocksOn code.

The ScrollBlocksOn code needs to be removed since passive event listeners
is the approach going forward.

BUG=489802
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1642093002

Cr-Commit-Position: refs/heads/master@{#372129}
20 files changed