Add MetalayerMode to the palette.

chrome/browser/ui/ash/palette_delegate_chromeos.h

Index: chrome/browser/ui/ash/palette_delegate_chromeos.h
diff --git a/chrome/browser/ui/ash/palette_delegate_chromeos.h b/chrome/browser/ui/ash/palette_delegate_chromeos.h
index ac059a826dfa75faa82ded295784a0087406edf3..33d09858080c9aca11c2a73bc1cc4402d6db773a 100644
--- a/chrome/browser/ui/ash/palette_delegate_chromeos.h
+++ b/chrome/browser/ui/ash/palette_delegate_chromeos.h
@@ -45,6 +45,9 @@ class PaletteDelegateChromeOS
   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;
 
   // user_manager::UserManager::UserSessionStateObserver:
   void ActiveUserChanged(const user_manager::User* active_user) override;