Partial revert of change to make Notification Center focusable after alt+shift+n

ui/message_center/views/message_center_view.cc

Index: ui/message_center/views/message_center_view.cc
diff --git a/ui/message_center/views/message_center_view.cc b/ui/message_center/views/message_center_view.cc
index 254b27203dea9566376a04749536741a86fc72ca..63a6132970fe7899bbbf5ebfbbc62819633a3d12 100644
--- a/ui/message_center/views/message_center_view.cc
+++ b/ui/message_center/views/message_center_view.cc
@@ -528,6 +528,16 @@ void MessageCenterView::Update(bool animate) {
   else
     SetVisibilityMode(Mode::NOTIFICATIONS, animate);
 
+  if (no_message_views) {
+    scroller_->SetFocusBehavior(FocusBehavior::NEVER);

[David Tseng, 2016/08/12 18:11:05]

Future note to xiyuan@
making this
+    scroller_->SetFocusBehavior(FocusBehavior::ACCESSIBLE_ONLY);
does nothing with ChromeVox on.

+  } else {
+#if defined(OS_MACOSX)
+    scroller_->SetFocusBehavior(FocusBehavior::ACCESSIBLE_ONLY);
+#else
+    scroller_->SetFocusBehavior(FocusBehavior::ALWAYS);
+#endif
+  }
+
   UpdateButtonBarStatus();
 
   if (focus_manager && focused_view)