Pass isLikelyToStartNewTask to onGestureStarted()

This ensures we immediately setRecentsAttachedToAppWindow(). As
mentioned in the bug, there was an edge case where we would animate
the attached state if the first move event passed the touch slop,
causing the adjacent task view to lag behind during the gesture.

Fixes: 159742520
Change-Id: Ie47bb84fdd3dbd69e3b74ca504d487fb9aedb551