Add UMA stats for pen palette

ash/common/system/chromeos/palette/palette_tool_manager.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_SYSTEM_CHROMEOS_PALETTE_PALETTE_TOOL_MANAGER_H_
 #define ASH_COMMON_SYSTEM_CHROMEOS_PALETTE_PALETTE_TOOL_MANAGER_H_
 
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 30 matching lines @@
 
     // Hide the palette (if shown).
     virtual void HidePalette() = 0;
 
     // Called when the active tool has changed.
     virtual void OnActiveToolChanged() = 0;
 
     // Return the window associated with this palette.
     virtual WmWindow* GetWindow() = 0;
 
+    // Record usage of each pen palette option.
+    virtual void RecordPaletteMetrics(ash::PaletteTrayOptions option) = 0;
+
    private:
     DISALLOW_COPY_AND_ASSIGN(Delegate);
   };
 
   // Creates the tool manager.
   PaletteToolManager(Delegate* delegate);
   ~PaletteToolManager() override;
 
   // Adds the given |tool| to the tool manager. The tool is assumed to be in a
   // deactivated state. This class takes ownership over |tool|.
@@ skipping 22 matching lines @@
   // Called when the views returned by CreateViews have been destroyed. This
   // should clear any (now) stale references.
   void NotifyViewsDestroyed();
 
  private:
   // PaleteTool::Delegate overrides.
   void EnableTool(PaletteToolId tool_id) override;
   void DisableTool(PaletteToolId tool_id) override;
   void HidePalette() override;
   WmWindow* GetWindow() override;
+  void RecordPaletteMetrics(ash::PaletteTrayOptions option) override;
 
   PaletteTool* FindToolById(PaletteToolId tool_id);
 
   // Unowned pointer to the delegate to provide external functionality.
   Delegate* delegate_;
 
   // Unowned pointer to the active tool / group.
   std::map<PaletteGroup, PaletteTool*> active_tools_;
 
   // Owned list of all tools.
   std::vector<std::unique_ptr<PaletteTool>> tools_;
 
   DISALLOW_COPY_AND_ASSIGN(PaletteToolManager);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_CHROMEOS_PALETTE_PALETTE_TOOL_MANAGER_H_