Auto merge of #22333 - asajeffrey:magicleap-mouse-pos-while-scrolling, r=jdm

Generate mouse move events as well as scroll events while scrolling

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Generate mouse move events as well as scroll events while scrolling. This is needed for sites which have their own semantics for moving the mouse with the button down.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because it's UI changes

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ports/libmlservo/src/lib.rs

@@ -200,10 +200,10 @@ pub unsafe extern "C" fn move_servo(servo: *mut ServoInstance, x: f32, y: f32) {
     // Servo's cursor was moved
     if let Some(servo) = servo.as_mut() {
         let point = DevicePoint::new(x, y);
-        let (new_state, window_event) = match servo.scroll_state {
+        let (new_state, window_events) = match servo.scroll_state {
             ScrollState::TriggerUp => (
                 ScrollState::TriggerUp,
-                WindowEvent::MouseWindowMoveEventClass(point),
+                vec![WindowEvent::MouseWindowMoveEventClass(point)],
             ),
             ScrollState::TriggerDown(start)
                 if (start - point).square_length() < DRAG_CUTOFF_SQUARED =>
@@ -212,23 +212,29 @@ pub unsafe extern "C" fn move_servo(servo: *mut ServoInstance, x: f32, y: f32) {
             },
             ScrollState::TriggerDown(start) => (
                 ScrollState::TriggerDragging(start, point),
+                vec![
+                    WindowEvent::MouseWindowMoveEventClass(point),
                     WindowEvent::Scroll(
                         ScrollLocation::Delta((point - start) * servo.scroll_scale),
                         start.to_i32(),
                         TouchEventType::Down,
                     ),
+                ],
             ),
             ScrollState::TriggerDragging(start, prev) => (
                 ScrollState::TriggerDragging(start, point),
+                vec![
+                    WindowEvent::MouseWindowMoveEventClass(point),
                     WindowEvent::Scroll(
                         ScrollLocation::Delta((point - prev) * servo.scroll_scale),
                         start.to_i32(),
                         TouchEventType::Move,
                     ),
+                ],
             ),
         };
         servo.scroll_state = new_state;
-        servo.servo.handle_events(vec![window_event]);
+        servo.servo.handle_events(window_events);
     }
 }