Merge to m48: Fix volume slider to emit value changed events and do not focus system tray it\

ash/system/audio/volume_view.cc

Index: ash/system/audio/volume_view.cc
diff --git a/ash/system/audio/volume_view.cc b/ash/system/audio/volume_view.cc
index 25f152125ce04a5ea5ac6cc2e1c1a3e533c65280..27b7ae966b056670d4d0b6f3c388b993fc243ad4 100644
--- a/ash/system/audio/volume_view.cc
+++ b/ash/system/audio/volume_view.cc
@@ -175,9 +175,6 @@ void VolumeView::SetVolumeLevel(float percent) {
   // slider value if the change is less than 1%.
   if (std::abs(percent-slider_->value()) < 0.01)
     return;
-  // The change in volume will be reflected via accessibility system events,
-  // so we prevent the UI event from being sent here.
-  slider_->set_enable_accessibility_events(false);
   slider_->SetValue(percent);
   // It is possible that the volume was (un)muted, but the actual volume level
   // did not change. In that case, setting the value of the slider won't