Bug 1563622 - Check the ftdc flag when hit-testing with WR. r=botond

Differential Revision: https://phabricator.services.mozilla.com/D37314

--HG--
extra : moz-landing-system : lando

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -2597,7 +2597,16 @@ already_AddRefed<AsyncPanZoomController> APZCTreeManager::GetAPZCAtPointWR(
   if (aOutLayersId) {
     *aOutLayersId = layersId;
   }
-  result = GetTargetAPZC(layersId, scrollId);
+  ScrollableLayerGuid guid{layersId, 0, scrollId};
+  if (RefPtr<HitTestingTreeNode> node =
+          GetTargetNode(guid, &GuidComparatorIgnoringPresShell)) {
+    MOZ_ASSERT(node->GetApzc()); // any node returned must have an APZC
+    result = node->GetApzc();
+    EventRegionsOverride flags = node->GetEventRegionsOverride();
+    if (flags & EventRegionsOverride::ForceDispatchToContent) {
+      hitInfo += CompositorHitTestFlags::eApzAwareListeners;
+    }
+  }
   if (!result) {
     // It falls back to the root
     MOZ_ASSERT(scrollId == ScrollableLayerGuid::NULL_SCROLL_ID);