Do not activate TrayBubbleView by default

ash/system/palette/palette_tray.h

 // Copyright 2016 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.
 
 #ifndef ASH_SYSTEM_PALETTE_PALETTE_TRAY_H_
 #define ASH_SYSTEM_PALETTE_PALETTE_TRAY_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 65 matching lines @@
 
  private:
   // ui::InputDeviceObserver:
   void OnTouchscreenDeviceConfigurationChanged() override;
   void OnStylusStateChanged(ui::StylusState stylus_state) override;
 
   // views::TrayBubbleView::Delegate:
   void BubbleViewDestroyed() override;
   void OnMouseEnteredView() override;
   void OnMouseExitedView() override;
+  void RegisterAccelerators(const std::vector<ui::Accelerator>& accelerators,
+                            views::TrayBubbleView* tray_bubble_view) override;
+  void UnregisterAllAccelerators(
+      views::TrayBubbleView* tray_bubble_view) override;
   base::string16 GetAccessibleNameForBubble() override;
+  bool ShouldEnableExtraKeyboardAccessibility() override;
   void HideBubble(const views::TrayBubbleView* bubble_view) override;
 
   // PaletteToolManager::Delegate:
   void OnActiveToolChanged() override;
   aura::Window* GetWindow() override;
 
   // Updates the tray icon from the palette tool manager.
   void UpdateTrayIcon();
 
   // Sets the icon to visible if the palette can be used.
@@ skipping 26 matching lines @@
   ScopedSessionObserver scoped_session_observer_;
 
   base::WeakPtrFactory<PaletteTray> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PaletteTray);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_PALETTE_PALETTE_TRAY_H_