[webkit-changes] [WebKit/WebKit] 2b5fad: Cherry-pick 92d0cdff8e9e. rdar://problem/103972021

[Simon Fraser]

  Branch: refs/heads/safari-7615.1.18-branch
  Home:   https://github.com/WebKit/WebKit
  Commit: 2b5fadaa8df47703491abcbd78db556a7ea3895b
      https://github.com/WebKit/WebKit/commit/2b5fadaa8df47703491abcbd78db556a7ea3895b
  Author: Simon Fraser <simon.fraser at apple.com>
  Date:   2023-01-09 (Mon, 09 Jan 2023)

  Changed paths:
    M Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingCoordinatorProxy.cpp

  Log Message:
  -----------
  Cherry-pick 92d0cdff8e9e. rdar://problem/103972021

    [UI-side compositing] Scrolling fails inside an element with a passive wheel event handler
    https://bugs.webkit.org/show_bug.cgi?id=250239
    rdar://103972021

    Reviewed by Tim Horton.

    When handling a wheel event inside a region with passive wheel event handlers, we'll
    get processing steps `[scrolling thread, main thread non-blocking DOM event dispatch]`.
    So we want to handle the scroll in the UI Process, but also send the wheel event to the
    web process for DOM event handling.

    So only early return in `RemoteScrollingCoordinatorProxy::handleWheelEvent()` when we
    don't see the "scrolling thread" step, and make sure we pass the steps to
    ScrollingTree::handleWheelEvent() so they get returned in the WheelEventHandlingResult.

    * Source/WebKit/UIProcess/RemoteLayerTree/RemoteScrollingCoordinatorProxy.cpp:
    (WebKit::RemoteScrollingCoordinatorProxy::handleWheelEvent):

    Canonical link: https://commits.webkit.org/258616@main

Canonical link: https://commits.webkit.org/258608.3@safari-7615.1.18-branch