Fix volume slider to emit value changed events and do not focus system tray item for transient views

ash/system/tray/system_tray.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.
 
 #include "ash/system/tray/system_tray.h"
 
 #include "ash/ash_switches.h"
 #include "ash/metrics/user_metrics_recorder.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shell.h"
@@ skipping 81 matching lines @@
     user::LoginStatus login_status =
         Shell::GetInstance()->system_tray_delegate()->GetUserLoginStatus();
     bubble_->InitView(anchor, login_status, init_params);
     bubble_wrapper_.reset(new TrayBubbleWrapper(tray, bubble_->bubble_view()));
     // The system bubble should not have an arrow.
     bubble_->bubble_view()->SetArrowPaintType(
         views::BubbleBorder::PAINT_NONE);
     is_persistent_ = is_persistent;
 
     // If ChromeVox is enabled, focus the default item if no item is focused.
-    if (Shell::GetInstance()->accessibility_delegate()->
-        IsSpokenFeedbackEnabled()) {
+    if (Shell::GetInstance()
+            ->accessibility_delegate()
+            ->IsSpokenFeedbackEnabled() &&
+        !is_persistent) {

[oshima, 2015/12/15 23:52:39]

Am I correct that we do not want to set the focus for solo volume/brightness
bubble so that it won't trigger the spoken feedback? 

can you update the comment?

[David Tseng, 2015/12/16 16:47:49]

That's correct. The semantics are important here. We want to get the
ui::AX_EVENT_VALUE_CHANGED events emitted by the slider, but not the focus
events.

Comment revised.

       bubble_->FocusDefaultIfNeeded();
     }
   }
 
   // Convenience accessors:
   SystemTrayBubble* bubble() const { return bubble_.get(); }
   SystemTrayBubble::BubbleType bubble_type() const {
     return bubble_->bubble_type();
   }
   TrayBubbleView* bubble_view() const { return bubble_->bubble_view(); }
@@ skipping 616 matching lines @@
   system_bubble_.reset();
   // When closing a system bubble with the alternate shelf layout, we need to
   // turn off the active tinting of the shelf.
   if (full_system_tray_menu_) {
     SetDrawBackgroundAsActive(false);
     full_system_tray_menu_ = false;
   }
 }
 
 }  // namespace ash