Add MetalayerMode to the palette.

ash/test/test_palette_delegate.h

Index: ash/test/test_palette_delegate.h
diff --git a/ash/test/test_palette_delegate.h b/ash/test/test_palette_delegate.h
index a572eb32b720c98e7b596ac7593394c9b430b3b8..739a1c6156a025b02b73548f07420a52de716ae8 100644
--- a/ash/test/test_palette_delegate.h
+++ b/ash/test/test_palette_delegate.h
@@ -51,6 +51,9 @@ class TestPaletteDelegate : public PaletteDelegate {
   void TakeScreenshot() override;
   void TakePartialScreenshot(const base::Closure& done) override;
   void CancelPartialScreenshot() override;
+  bool HasMetalayer() override;
+  void ShowMetalayer(const base::Closure& done) override;
+  void HideMetalayer() override;
 
   int create_note_count_ = 0;
   int has_note_app_count_ = 0;