Do not activate system tray bubble by default

ash/common/system/tray/hover_highlight_view.cc

 // Copyright 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/common/system/tray/hover_highlight_view.h"
 
 #include "ash/common/system/tray/fixed_sized_image_view.h"
 #include "ash/common/system/tray/tray_constants.h"
 #include "ash/common/system/tray/view_click_listener.h"
 #include "ui/accessibility/ax_view_state.h"
@@ skipping 15 matching lines @@
 const gfx::FontList& GetFontList(bool highlight) {
   return ui::ResourceBundle::GetSharedInstance().GetFontList(
       highlight ? ui::ResourceBundle::BoldFont : ui::ResourceBundle::BaseFont);
 }
 
 }  // namespace
 
 namespace ash {
 
 HoverHighlightView::HoverHighlightView(ViewClickListener* listener)
-    : listener_(listener), highlight_color_(kHoverBackgroundColor) {
+    : ActionableView(nullptr),
+      listener_(listener),
+      highlight_color_(kHoverBackgroundColor) {
   set_notify_enter_exit_on_child(true);
 }
 
 HoverHighlightView::~HoverHighlightView() {}
 
 bool HoverHighlightView::GetTooltipText(const gfx::Point& p,
                                         base::string16* tooltip) const {
   if (tooltip_.empty())
     return false;
   *tooltip = tooltip_;
@@ skipping 218 matching lines @@
 void HoverHighlightView::OnPaintBackground(gfx::Canvas* canvas) {
   canvas->DrawColor(hover_ ? highlight_color_ : default_color_);
 }
 
 void HoverHighlightView::OnFocus() {
   ScrollRectToVisible(gfx::Rect(gfx::Point(), size()));
   ActionableView::OnFocus();
 }
 
 }  // namespace ash