Add MetalayerMode to the palette.

ash/system/palette/palette_ids.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_IDS_H_
 #define ASH_SYSTEM_PALETTE_PALETTE_IDS_H_
 
 #include <string>
 
 #include "ash/ash_export.h"
 
 namespace ash {
 
 // Palette tools are grouped into different categories. Each tool corresponds to
 // exactly one group, and at most one tool can be active per group. Actions are
 // actions the user wants to do, such as take a screenshot, and modes generally
 // change OS behavior, like showing a laser pointer instead of a cursor. A mode
 // is active until the user completes the action or disables it.
 enum class PaletteGroup { ACTION, MODE };
 
 enum class PaletteToolId {
   NONE,
   CREATE_NOTE,
   CAPTURE_REGION,
   CAPTURE_SCREEN,
   LASER_POINTER,
   MAGNIFY,
+  METALAYER,
 };
 
 // Usage of each pen palette option. This enum is used to back an UMA histogram
 // and should be treated as append-only.
 enum PaletteTrayOptions {
   PALETTE_CLOSED_NO_ACTION = 0,
   PALETTE_SETTINGS_BUTTON,
   PALETTE_HELP_BUTTON,
   PALETTE_CAPTURE_REGION,
   PALETTE_CAPTURE_SCREEN,
   PALETTE_NEW_NOTE,
   PALETTE_MAGNIFY,
   PALETTE_LASER_POINTER,
+  PALETTE_METALAYER,
   PALETTE_OPTIONS_COUNT
 };
 
 // Type of palette mode cancellation. This enum is used to back an UMA histogram
 // and should be treated as append-only.
 enum PaletteModeCancelType {
   PALETTE_MODE_LASER_POINTER_CANCELLED = 0,
   PALETTE_MODE_LASER_POINTER_SWITCHED,
   PALETTE_MODE_MAGNIFY_CANCELLED,
   PALETTE_MODE_MAGNIFY_SWITCHED,
   PALETTE_MODE_CANCEL_TYPE_COUNT
 };
 
 // Helper functions that convert PaletteToolIds and PaletteGroups to strings.
 ASH_EXPORT std::string PaletteToolIdToString(PaletteToolId tool_id);
 ASH_EXPORT std::string PaletteGroupToString(PaletteGroup group);
 
 // Helper functions that convert PaletteToolIds to PaletteTrayOptions.
 ASH_EXPORT PaletteTrayOptions
 PaletteToolIdToPaletteTrayOptions(PaletteToolId tool_id);
 
 // Helper functions that convert PaletteToolIds to PaletteModeCancelType.
 ASH_EXPORT PaletteModeCancelType
 PaletteToolIdToPaletteModeCancelType(PaletteToolId tool_id, bool is_switched);
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_PALETTE_PALETTE_IDS_H_