Add pref to enable/disable palette tray.

ash/common/test/test_palette_delegate.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_COMMON_TEST_TEST_PALETTE_DELEGATE_H_
 #define ASH_COMMON_TEST_TEST_PALETTE_DELEGATE_H_
 
 #include "ash/common/palette_delegate.h"
 #include "base/macros.h"
 
@@ skipping 18 matching lines @@
   }
 
   void set_has_note_app(bool has_note_app) { has_note_app_ = has_note_app; }
 
   void set_should_auto_open_palette(bool should_auto_open_palette) {
     should_auto_open_palette_ = should_auto_open_palette;
   }
 
  private:
   // PaletteDelegate:
+  std::unique_ptr<EnableListenerSubscription> AddPaletteEnableListener(
+      const EnableListener& on_state_changed) override;
   void CreateNote() override;
   bool HasNoteApp() override;
   void SetPartialMagnifierState(bool enabled) override;
   void SetStylusStateChangedCallback(
       const OnStylusStateChangedCallback& on_stylus_state_changed) override;
   bool ShouldAutoOpenPalette() override;
   void TakeScreenshot() override;
   void TakePartialScreenshot() override;
 
   int create_note_count_ = 0;
   int has_note_app_count_ = 0;
   bool partial_magnifier_state_ = false;
   int take_screenshot_count_ = 0;
   int take_partial_screenshot_count_ = 0;
   bool has_note_app_ = false;
   bool should_auto_open_palette_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(TestPaletteDelegate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_TEST_TEST_PALETTE_DELEGATE_H_