Do not activate TrayBubbleView by default

ash/system/tray/system_tray_bubble.cc

Index: ash/system/tray/system_tray_bubble.cc
diff --git a/ash/system/tray/system_tray_bubble.cc b/ash/system/tray/system_tray_bubble.cc
index bf94470ed85f0c75f6784d3d8513fc6c2e1cc0de..331724d542bae74f45780dacf4c76e21b01dc4e7 100644
--- a/ash/system/tray/system_tray_bubble.cc
+++ b/ash/system/tray/system_tray_bubble.cc
@@ -84,7 +84,7 @@ SystemTrayBubble::~SystemTrayBubble() {
   DestroyItemViews();
   // Reset the host pointer in bubble_view_ in case its destruction is deferred.
   if (bubble_view_)
-    bubble_view_->reset_delegate();
+    bubble_view_->ResetDelegate();
 }
 
 void SystemTrayBubble::UpdateView(
@@ -211,14 +211,7 @@ void SystemTrayBubble::InitView(views::View* anchor,
 }
 
 void SystemTrayBubble::FocusDefaultIfNeeded() {
-  views::FocusManager* manager = bubble_view_->GetFocusManager();
-  if (!manager || manager->GetFocusedView())
-    return;
-
-  views::View* view =
-      manager->GetNextFocusableView(nullptr, nullptr, false, false);
-  if (view)
-    view->RequestFocus();
+  bubble_view_->FocusDefaultIfNeeded();
 }
 
 void SystemTrayBubble::DestroyItemViews() {