Use ui::AX_EVENT_SELECTION to read aloud omnibox suggestion answers.

chrome/browser/ui/views/omnibox/omnibox_result_view.cc

 // 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.
 
 // For WinDDK ATL compatibility, these ATL headers must come first.
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <atlbase.h>  // NOLINT
 #include <atlwin.h>  // NOLINT
@@ skipping 276 matching lines @@
 }
 
 void OmniboxResultView::OnSelected() {
   DCHECK_EQ(SELECTED, GetState());
 
   // Notify assistive technology when results with answers attached are
   // selected. The non-answer text is already accessible as a consequence of
   // updating the text in the omnibox but this alert and GetAccessibleNodeData
   // below make the answer contents accessible.
   if (match_.answer)
-    NotifyAccessibilityEvent(ui::AX_EVENT_ALERT, true);
+    NotifyAccessibilityEvent(ui::AX_EVENT_SELECTION, true);
 }
 
 gfx::Size OmniboxResultView::GetPreferredSize() const {
   int height = GetTextHeight() + (2 * GetVerticalMargin());
   if (match_.answer)
     height += GetAnswerHeight() + kVerticalPadding;
   return gfx::Size(0, height);
 }
 
 void OmniboxResultView::GetAccessibleNodeData(ui::AXNodeData* node_data) {
@@ skipping 494 matching lines @@
   destination->AppendText(text);
   const TextStyle& text_style = GetTextStyle(text_type);
   // TODO(dschuyler): follow up on the problem of different font sizes within
   // one RenderText.  Maybe with destination->SetFontList(...).
   destination->ApplyWeight(
       is_bold ? gfx::Font::Weight::BOLD : gfx::Font::Weight::NORMAL, range);
   destination->ApplyColor(
       GetNativeTheme()->GetSystemColor(text_style.colors[GetState()]), range);
   destination->ApplyBaselineStyle(text_style.baseline, range);
 }