Newly created live regions should fire a private notification on the Mac.

content/browser/accessibility/browser_accessibility_manager_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/accessibility/browser_accessibility_manager_mac.h"
 
 #import "base/mac/mac_util.h"
 #import "base/mac/sdk_forward_declarations.h"
 #include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
@@ skipping 47 matching lines @@
 };
 
 NSString* const NSAccessibilityAutocorrectionOccurredNotification =
     @"AXAutocorrectionOccurred";
 NSString* const NSAccessibilityLayoutCompleteNotification =
     @"AXLayoutComplete";
 NSString* const NSAccessibilityLoadCompleteNotification =
     @"AXLoadComplete";
 NSString* const NSAccessibilityInvalidStatusChangedNotification =
     @"AXInvalidStatusChanged";
+NSString* const NSAccessibilityLiveRegionCreatedNotification =
+    @"AXLiveRegionCreated";
 NSString* const NSAccessibilityLiveRegionChangedNotification =
     @"AXLiveRegionChanged";
 NSString* const NSAccessibilityExpandedChanged =
     @"AXExpandedChanged";
 NSString* const NSAccessibilityMenuItemSelectedNotification =
     @"AXMenuItemSelected";
 
 // Attributes used for NSAccessibilitySelectedTextChangedNotification and
 // NSAccessibilityValueChangedNotification.
 NSString* const NSAccessibilityTextStateChangeTypeKey =
@@ skipping 176 matching lines @@
         if (!root)
           return;
 
         NSAccessibilityPostNotificationWithUserInfo(
             native_node, mac_notification, user_info);
         NSAccessibilityPostNotificationWithUserInfo(
             ToBrowserAccessibilityCocoa(root), mac_notification, user_info);
         return;
       }
       break;
-    // TODO(nektar): Need to add an event for live region created.
+    case ui::AX_EVENT_ALERT:
+      mac_notification = NSAccessibilityLiveRegionCreatedNotification;
+      // A live region created notification must be followed by a live region
+      // changed notification.
     case ui::AX_EVENT_LIVE_REGION_CHANGED:
       mac_notification = NSAccessibilityLiveRegionChangedNotification;
       break;
     case ui::AX_EVENT_ROW_COUNT_CHANGED:
       mac_notification = NSAccessibilityRowCountChangedNotification;
       break;
     case ui::AX_EVENT_ROW_EXPANDED:
       mac_notification = NSAccessibilityRowExpandedNotification;
       break;
     case ui::AX_EVENT_ROW_COLLAPSED:
       mac_notification = NSAccessibilityRowCollapsedNotification;
       break;
     // TODO(nektar): Add events for busy.
     case ui::AX_EVENT_EXPANDED_CHANGED:
       mac_notification = NSAccessibilityExpandedChanged;
       break;
     // TODO(nektar): Support menu open/close notifications.
     case ui::AX_EVENT_MENU_LIST_ITEM_SELECTED:
       mac_notification = NSAccessibilityMenuItemSelectedNotification;
       break;
 
     // These events are not used on Mac for now.
-    case ui::AX_EVENT_ALERT:
     case ui::AX_EVENT_TEXT_CHANGED:
     case ui::AX_EVENT_CHILDREN_CHANGED:
     case ui::AX_EVENT_MENU_LIST_VALUE_CHANGED:
     case ui::AX_EVENT_SCROLL_POSITION_CHANGED:
     case ui::AX_EVENT_SCROLLED_TO_ANCHOR:
     case ui::AX_EVENT_ARIA_ATTRIBUTE_CHANGED:
     case ui::AX_EVENT_LOCATION_CHANGED:
       return;
 
     // Deprecated events.
@@ skipping 78 matching lines @@
   bool created_live_region = false;
   for (size_t i = 0; i < changes.size(); ++i) {
     if (changes[i].type != NODE_CREATED && changes[i].type != SUBTREE_CREATED)
       continue;
 
     const ui::AXNode* changed_node = changes[i].node;
     DCHECK(changed_node);
     BrowserAccessibility* obj = GetFromAXNode(changed_node);
     if (obj && obj->HasStringAttribute(ui::AX_ATTR_LIVE_STATUS)) {
       created_live_region = true;
-      break;
+      NotifyAccessibilityEvent(BrowserAccessibilityEvent::FromTreeChange,
+                               ui::AX_EVENT_ALERT, obj);
     }
   }
 
   if (!created_live_region)
     return;
 
   // This code is to work around a bug in VoiceOver, where a new live

[dmazzoni, 2016/08/08 18:49:05]

I think you should try deleting the following block of code.
My guess is that it's getting in the way of VoiceOver
speaking a live region created event because it destroys
and recreates the native accessibility tree.

   // region that gets added is ignored. VoiceOver seems to only scan the
   // page for live regions once. By recreating the NSAccessibility
   // object for the root of the tree, we force VoiceOver to clear out its
   // internal state and find newly-added live regions this time.
   BrowserAccessibilityMac* root =
       static_cast<BrowserAccessibilityMac*>(GetRoot());
   if (root) {
     root->RecreateNativeObject();
     NotifyAccessibilityEvent(
         BrowserAccessibilityEvent::FromTreeChange,
@@ skipping 57 matching lines @@
   }
 
   return @{
     NSAccessibilityTextStateChangeTypeKey : @(AXTextStateChangeTypeEdit),
     NSAccessibilityTextChangeValues : changes,
     NSAccessibilityTextChangeElement : native_node
   };
 }
 
 }  // namespace content