Add UMA stats for pen palette

ash/common/system/chromeos/palette/palette_tray.h

Index: ash/common/system/chromeos/palette/palette_tray.h
diff --git a/ash/common/system/chromeos/palette/palette_tray.h b/ash/common/system/chromeos/palette/palette_tray.h
index ad5dd9ecc66edda9425a804b3885bb8130a5861f..574a28e935276be586931d4ddac38eaa90231d7b 100644
--- a/ash/common/system/chromeos/palette/palette_tray.h
+++ b/ash/common/system/chromeos/palette/palette_tray.h
@@ -57,6 +57,7 @@ class ASH_EXPORT PaletteTray : public TrayBackgroundView,
 
   // PaletteToolManager::Delegate:
   void HidePalette() override;
+  void RecordPaletteMetrics(ash::PaletteTrayOptions option) override;
 
   // Returns true if the shelf should not autohide.
   bool ShouldBlockShelfAutoHide() const;
@@ -113,6 +114,13 @@ class ASH_EXPORT PaletteTray : public TrayBackgroundView,
   // Weak pointer, will be parented by TrayContainer for its lifetime.
   views::ImageView* icon_;
 
+  // Used to indicate whether the palette is automatically opened by a stylus
+  // eject event.
+  bool is_palette_auto_opened = false;

[jdufault, 2016/09/02 21:54:30]

What about is_bubble_auto_opened_?

[xiaoyinh(OOO Sep 11-29), 2016/09/06 17:40:05]

Done.

+
+  // Number of actions in pen palette.
+  int num_actions_in_palette = 0;

[jdufault, 2016/09/02 21:54:30]

num_actions_in_bubble_?

[xiaoyinh(OOO Sep 11-29), 2016/09/06 17:40:05]

Done.

+
   base::WeakPtrFactory<PaletteTray> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PaletteTray);