Bug 1638594 - Use visual coordinates when hit testing in a chrome document. r=tnikkel, a=jcristau

It does not make sense to ask for layout coordinates relative to
a chrome document. If the chrome document has a zoomed (RCD)
descendant in the same process, this means we do not apply the
visual-to-layout transform when later entering the RCD.

Depends on D79588

Differential Revision: https://phabricator.services.mozilla.com/D79589

layout/base/PresShell.cpp

@@ -6974,9 +6974,13 @@ nsIFrame* PresShell::EventHandler::GetFrameToHandleNonTouchEvent(
   MOZ_ASSERT(aGUIEvent->mClass != eTouchEventClass);
 
   ViewportType viewportType = ViewportType::Layout;
-  if (aRootFrameToHandleEvent->Type() == LayoutFrameType::Viewport &&
-      aRootFrameToHandleEvent->PresContext()->IsRootContentDocument()) {
-    viewportType = ViewportTypeForInputEventsRelativeToRoot();
+  if (aRootFrameToHandleEvent->Type() == LayoutFrameType::Viewport) {
+    nsPresContext* pc = aRootFrameToHandleEvent->PresContext();
+    if (pc->IsChrome()) {
+      viewportType = ViewportType::Visual;
+    } else if (pc->IsRootContentDocument()) {
+      viewportType = ViewportTypeForInputEventsRelativeToRoot();
+    }
   }
   RelativeTo relativeTo{aRootFrameToHandleEvent, viewportType};
   nsPoint eventPoint =