Backed out changeset 846e436ca1c2 (bug 1870512) for causing automation.py related Windows failures CLOSED TREE

accessible/windows/msaa/MsaaDocAccessible.cpp

@@ -94,6 +94,29 @@ MsaaDocAccessible::get_accParent(
        (nsWinUtils::IsWindowEmulationStarted() &&
         nsCoreUtils::IsTopLevelContentDocInProcess(docAcc->DocumentNode())))) {
     HWND hwnd = static_cast<HWND>(docAcc->GetNativeWindow());
+    if (hwnd && !docAcc->ParentDocument()) {
+      nsIFrame* frame = docAcc->GetFrame();
+      if (frame) {
+        nsIWidget* widget = frame->GetNearestWidget();
+        if (widget->GetWindowType() == widget::WindowType::Child &&
+            !widget->GetParent()) {
+          // Bug 1427304: Windows opened with popup=yes (such as the WebRTC
+          // sharing indicator) get two HWNDs. The root widget is associated
+          // with the inner HWND, but the outer HWND still answers to
+          // WM_GETOBJECT queries. This means that getting the parent of the
+          // oleacc window accessible for the inner HWND returns this
+          // root accessible. Thus, to avoid a loop, we must never return the
+          // oleacc window accessible for the inner HWND. Instead, we use the
+          // outer HWND here.
+          HWND parentHwnd = ::GetParent(hwnd);
+          if (parentHwnd) {
+            MOZ_ASSERT(::GetWindowLongW(parentHwnd, GWL_STYLE) & WS_POPUP,
+                       "Parent HWND should be a popup!");
+            hwnd = parentHwnd;
+          }
+        }
+      }
+    }
     if (hwnd &&
         SUCCEEDED(::CreateStdAccessibleObject(
             hwnd, OBJID_WINDOW, IID_IAccessible, (void**)ppdispParent))) {