Bug 304484. Expose alerts, prompts and message boxes as ROLE_ALERT so screen readers have a cue to speak the entire dialog when it appears. r=mconnor

toolkit/components/alerts/resources/content/alert.xul

@@ -41,6 +41,9 @@
 <window id="alertNotification"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
         windowtype="alert:alert"
+        xmlns:xhtml2="http://www.w3.org/TR/xhtml2"
+        xmlns:wairole="http://www.w3.org/2005/01/wai-rdf/GUIRoleTaxonomy#"
+        xhtml2:role="wairole:alert"
         align="start"
         onload="onAlertLoad()">
   

toolkit/content/commonDialog.xul

@@ -6,6 +6,9 @@
 
 <dialog id="commonDialog"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" 
+        xmlns:xhtml2="http://www.w3.org/TR/xhtml2"
+        xmlns:wairole="http://www.w3.org/2005/01/wai-rdf/GUIRoleTaxonomy#"
+        xhtml2:role="wairole:alert"
         onload="commonDialogOnLoad();"
         ondialogaccept="return commonDialogOnAccept();"
         ondialogextra1="return commonDialogOnExtra1();"