Allow OHOS servoshell to have a simple multiple tab implementation. (#36891)

Currently we just pause the compositor and replace the window in it
while having separate bookkeeping to remember which window belongs to
which tab.
Currently there are no tests for OHOS, so we cannot test the changes.

---------

Signed-off-by: Narfinger <Narfinger@users.noreply.github.com>
Co-authored-by: Jonathan Schwender <55576758+jschwe@users.noreply.github.com>

components/compositing/touch.rs

@@ -292,6 +292,10 @@ impl TouchHandler {
             .expect("Current Touch sequence does not exist")
     }
 
+    fn try_get_current_touch_sequence_mut(&mut self) -> Option<&mut TouchSequenceInfo> {
+        self.touch_sequence_map.get_mut(&self.current_sequence_id)
+    }
+
     pub(crate) fn get_touch_sequence(&self, sequence_id: TouchSequenceId) -> &TouchSequenceInfo {
         self.touch_sequence_map
             .get(&sequence_id)
@@ -374,7 +378,12 @@ impl TouchHandler {
         id: TouchId,
         point: Point2D<f32, DevicePixel>,
     ) -> TouchMoveAction {
-        let touch_sequence = self.get_current_touch_sequence_mut();
+        // As `TouchHandler` is per `WebViewRenderer` which is per `WebView` we might get a Touch Sequence Move that
+        // started with a down on a different webview. As the touch_sequence id is only changed on touch_down this
+        // move event gets a touch id which is already cleaned up.
+        let Some(touch_sequence) = self.try_get_current_touch_sequence_mut() else {
+            return TouchMoveAction::NoAction;
+        };
         let idx = match touch_sequence
             .active_touch_points
             .iter_mut()
@@ -529,7 +538,10 @@ impl TouchHandler {
     }
 
     pub fn on_touch_cancel(&mut self, id: TouchId, _point: Point2D<f32, DevicePixel>) {
-        let touch_sequence = self.get_current_touch_sequence_mut();
+        // A similar thing with touch move can happen here where the event is coming from a different webview.
+        let Some(touch_sequence) = self.try_get_current_touch_sequence_mut() else {
+            return;
+        };
         match touch_sequence
             .active_touch_points
             .iter()

components/shared/embedder/input_events.rs

@@ -182,6 +182,7 @@ pub enum TouchEventType {
 pub struct TouchId(pub i32);
 
 /// An ID for a sequence of touch events between a `Down` and the `Up` or `Cancel` event.
+/// The ID is the same for all events between `Down` and `Up` or `Cancel`
 #[repr(transparent)]
 #[derive(Clone, Copy, Debug, Default, Deserialize, Eq, Hash, PartialEq, Serialize)]
 pub struct TouchSequenceId(u32);