Fix stylus tools palette.

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 15 matching lines @@
 class Widget;
 }
 
 namespace ash {
 
 class TrayBubbleWrapper;
 class PaletteToolManager;
 
 // The PaletteTray shows the palette in the bottom area of the screen. This
 // class also controls the lifetime for all of the tools available in the
-// palette.
+// palette. PaletteTray has one instance per-display. It is only made visible if
+// the display is primary and if the device has stylus hardware.
 class ASH_EXPORT PaletteTray : public TrayBackgroundView,
                                public SessionObserver,
                                public ShellObserver,
                                public PaletteToolManager::Delegate,
                                public ui::InputDeviceEventObserver,
                                public views::TrayBubbleView::Delegate {
  public:
   explicit PaletteTray(WmShelf* wm_shelf);
   ~PaletteTray() override;
 
@@ skipping 80 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_