Add feature flag for scrollbar scroll injecting gestures

Given that there were a couple regressions the first time I changed this
behavior for scrollbar presses (see and the revert,, I'm introducing a feature flag so that we can
have a kill switch.,,

Bug: 954007
Change-Id: I635c5f39a798986c820287c47474f8b80a473307
Commit-Queue: Daniel Libby <>
Reviewed-by: Daniel Cheng <>
Reviewed-by: David Bokan <>
Cr-Commit-Position: refs/heads/master@{#662075}
2 files changed