chromeos: Simplify ShutdownPolicyHandler

ash/common/system/tray/system_tray_delegate.h

Index: ash/common/system/tray/system_tray_delegate.h
diff --git a/ash/common/system/tray/system_tray_delegate.h b/ash/common/system/tray/system_tray_delegate.h
index 61ff9b64a00003749c9f0f612de348b1fab887f3..015576f87b214ea5bb775b02e26a6de9cd134673 100644
--- a/ash/common/system/tray/system_tray_delegate.h
+++ b/ash/common/system/tray/system_tray_delegate.h
@@ -76,8 +76,6 @@ class CastConfigDelegate;
 class NetworkingConfigDelegate;
 class VPNDelegate;
 
-using RebootOnShutdownCallback = base::Callback<void(bool)>;
-
 // SystemTrayDelegate is intended for delegating tasks in the System Tray to the
 // application (e.g. Chrome). These tasks should be limited to application
 // (browser) specific tasks. For non application specific tasks, where possible,
@@ -232,8 +230,9 @@ class ASH_EXPORT SystemTrayDelegate {
 
   // Determines whether the device is automatically rebooted when shut down as
   // specified by the device policy |DeviceRebootOnShutdown|. This function
-  // asynchronously calls |callback| once a trusted policy becomes available.
-  virtual void ShouldRebootOnShutdown(const RebootOnShutdownCallback& callback);
+  // notifies the shutdown policy observers added above once a trusted policy
+  // becomes available.
+  virtual void CheckIfRebootOnShutdown();
 
   // Returns VPNDelegate. May return nullptr.
   virtual VPNDelegate* GetVPNDelegate() const;