Let ChromeVox read the toast contents when it's updated.

ui/message_center/views/toast_contents_view.cc

 // Copyright (c) 2013 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 "ui/message_center/views/toast_contents_view.h"
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 66 matching lines @@
     params.top_level = true;
   params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
   params.delegate = this;
   views::Widget* widget = new views::Widget();
   widget->set_focus_on_creation(false);
   widget->Init(params);
   return widget;
 }
 
 void ToastContentsView::SetContents(MessageView* view) {
+  bool already_has_contents = child_count() > 0;
   RemoveAllChildViews(true);
   AddChildView(view);
   preferred_size_ = GetToastSizeForView(view);
   Layout();
+  // If it has the contents already, this invocation means an update of the
+  // popup toast, and the new contents should be read through a11y feature.
+  if (already_has_contents)
+    NotifyAccessibilityEvent(ui::AccessibilityTypes::EVENT_FOCUS, false);
 }
 
 void ToastContentsView::RevealWithAnimation(gfx::Point origin) {
   // Place/move the toast widgets. Currently it stacks the widgets from the
   // right-bottom of the work area.
   // TODO(mukai): allow to specify the placement policy from outside of this
   // class. The policy should be specified from preference on Windows, or
   // the launcher alignment on ChromeOS.
   origin_ = gfx::Point(origin.x() - preferred_size_.width(),
                        origin.y() - preferred_size_.height());
@@ skipping 194 matching lines @@
 }
 
 gfx::Rect ToastContentsView::GetClosedToastBounds(gfx::Rect bounds) {
   return gfx::Rect(bounds.x() + bounds.width() - kClosedToastWidth,
                    bounds.y(),
                    kClosedToastWidth,
                    bounds.height());
 }
 
 }  // namespace message_center