a11y/Mac: Add screenreader support for SubtleNotificationView announcements.

chrome/browser/ui/views/exclusive_access_bubble_views.cc

Index: chrome/browser/ui/views/exclusive_access_bubble_views.cc
diff --git a/chrome/browser/ui/views/exclusive_access_bubble_views.cc b/chrome/browser/ui/views/exclusive_access_bubble_views.cc
index b67c9378e3143485cdbf322024e9a3a57890a220..b5d33d448254e86821778ca7d051af3dac44624a 100644
--- a/chrome/browser/ui/views/exclusive_access_bubble_views.cc
+++ b/chrome/browser/ui/views/exclusive_access_bubble_views.cc
@@ -125,6 +125,8 @@ void ExclusiveAccessBubbleViews::UpdateContent(
   StopWatchingMouse();
 
   UpdateMouseWatcher();
+
+  view_->NotifyAccessibilityEvent(ui::AX_EVENT_TEXT_CHANGED, true);
 }
 
 void ExclusiveAccessBubbleViews::RepositionIfVisible() {
@@ -257,6 +259,8 @@ void ExclusiveAccessBubbleViews::Hide() {
 void ExclusiveAccessBubbleViews::Show() {
   animation_->SetSlideDuration(kSlideInDurationMs);
   animation_->Show();
+
+  view_->NotifyAccessibilityEvent(ui::AX_EVENT_ALERT, true);
 }
 
 bool ExclusiveAccessBubbleViews::IsAnimating() {