Bug 1368103 - Use DOM doc visibilityState to determine if a tab is hidden. r=surkov

accessible/generic/Accessible.cpp

@@ -335,6 +335,10 @@ Accessible::VisibilityState()
   if (!frame->StyleVisibility()->IsVisible())
     return states::INVISIBLE;
 
+  // Offscreen state if the document's visibility state is not visible.
+  if (Document()->IsHidden())
+    return states::OFFSCREEN;
+
   nsIFrame* curFrame = frame;
   do {
     nsView* view = curFrame->GetView();

accessible/generic/DocAccessible.h

@@ -137,6 +137,11 @@ public:
       (mDocumentNode->IsShowing() || HasLoadState(eDOMLoaded));
   }
 
+  bool IsHidden() const
+  {
+    return mDocumentNode->Hidden();
+  }
+
   /**
    * Document load states.
    */