Uses the activedescendant_changed event received from Blink to fire the right focus event

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 114 matching lines @@
       1 << ui::AX_STATE_READ_ONLY;
   ui::AXTreeUpdate update;
   update.root_id = empty_document.id;
   update.nodes.push_back(empty_document);
   return update;
 }
 
 BrowserAccessibility* BrowserAccessibilityManagerMac::GetFocus() {
   // On Mac, list boxes should always get focus on the whole list, otherwise
   // information about the number of selected items will never be reported.
+  // For combo boxes, focus should stay on the combo box so the user will not be

[dmazzoni, 2016/04/29 20:55:54]

Consider doing this only for combo boxes where IsEditableText is true?

Sometimes people put role="combobox" on something that's more like a single-item
listbox and it maybe shouldn't behave the same.

+  // taken out of the combo box while typing.
   BrowserAccessibility* node = BrowserAccessibilityManager::GetFocus();
-  if (node && node->GetRole() == ui::AX_ROLE_LIST_BOX)
+  if (node && (node->GetRole() == ui::AX_ROLE_LIST_BOX ||
+               node->GetRole() == ui::AX_ROLE_COMBO_BOX)) {
     return node;
+  }
 
   // For other roles, follow the active descendant.
   return GetActiveDescendantFocus(node);
 }
 
 void BrowserAccessibilityManagerMac::NotifyAccessibilityEvent(
     ui::AXEvent event_type,
     BrowserAccessibility* node) {
   if (!node->IsNative())
     return;
 
-  if (event_type == ui::AX_EVENT_FOCUS) {
-    BrowserAccessibility* active_descendant = GetActiveDescendantFocus(node);
-    if (active_descendant)
-      node = active_descendant;
-
-    if (node->GetRole() == ui::AX_ROLE_LIST_BOX_OPTION &&
-        node->HasState(ui::AX_STATE_SELECTED) &&
-        node->GetParent() &&
-        node->GetParent()->GetRole() == ui::AX_ROLE_LIST_BOX) {
-      node = node->GetParent();
-      SetFocus(*node);
-    }
-  }
-
   auto native_node = ToBrowserAccessibilityCocoa(node);
   DCHECK(native_node);
 
   // Refer to |AXObjectCache::postPlatformNotification| in WebKit source code.
   NSString* mac_notification;
   switch (event_type) {
     case ui::AX_EVENT_ACTIVEDESCENDANTCHANGED:
       if (node->GetRole() == ui::AX_ROLE_TREE) {
         mac_notification = NSAccessibilitySelectedRowsChangedNotification;
       } else if (node->GetRole() == ui::AX_ROLE_COMBO_BOX) {
         // Even though the selected item in the combo box has changed, we don't
         // want to post a focus change because this will take the focus out of
         // the combo box where the user might be typing.
         mac_notification = NSAccessibilitySelectedChildrenChangedNotification;
       } else {
-        mac_notification = NSAccessibilityFocusedUIElementChangedNotification;
+        // In all other cases we should post
+        // |NSAccessibilityFocusedUIElementChangedNotification|, but this is
+        // handled elsewhere.
+        return;
       }
       break;
     case ui::AX_EVENT_AUTOCORRECTION_OCCURED:
       mac_notification = NSAccessibilityAutocorrectionOccurredNotification;
       break;
     case ui::AX_EVENT_FOCUS:
       mac_notification = NSAccessibilityFocusedUIElementChangedNotification;
       break;
     case ui::AX_EVENT_LAYOUT_COMPLETE:
       mac_notification = NSAccessibilityLayoutCompleteNotification;
@@ skipping 263 matching lines @@
   }
 
   return @{
     NSAccessibilityTextStateChangeTypeKey : @(AXTextStateChangeTypeEdit),
     NSAccessibilityTextChangeValues : changes,
     NSAccessibilityTextChangeElement : native_node
   };
 }
 
 }  // namespace content