Fix Voice Guidance reads iframe when added to DOM

Backported from:
#820

Author: filipe-norte-red

Source/WebCore/accessibility/atk/WebKitAccessible.cpp

@@ -745,7 +745,13 @@ static AtkRole atkRole(AccessibilityObject* coreObject)
     case AccessibilityRole::UserInterfaceTooltip:
         return ATK_ROLE_TOOL_TIP;
     case AccessibilityRole::WebArea:
-        return ATK_ROLE_DOCUMENT_WEB;
+    {
+        WebCore::Frame *frame = coreObject->frame();
+        if (frame)
+           return frame->WebCore::Frame::isMainFrame() ? ATK_ROLE_DOCUMENT_WEB : ATK_ROLE_DOCUMENT_FRAME;
+        else
+           return ATK_ROLE_DOCUMENT_WEB;
+    }
     case AccessibilityRole::WebApplication:
         return ATK_ROLE_EMBEDDED;
     case AccessibilityRole::ApplicationLog: