The user interaction triggered `scroll` event was initially implemented
in https://github.com/servo/servo/pull/36687.
In triggering the `scroll` event, the event should be batched and
triggered within update the rendering. This serves as a preparatory PR
for the JS API triggered `scroll` event.
Part of: #31665
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Signed-off-by: Jo Steven Novaryo <jo.steven.novaryo@huawei.com>