ObserverList::HasObserver now takes a const pointer.

chromeos/dbus/system_clock_client.h

Index: chromeos/dbus/system_clock_client.h
diff --git a/chromeos/dbus/system_clock_client.h b/chromeos/dbus/system_clock_client.h
index 1757853950f57f68eb23ecd1dacd9b2e68188426..8380ff1de3808304eefd9405a983bca9afab0c70 100644
--- a/chromeos/dbus/system_clock_client.h
+++ b/chromeos/dbus/system_clock_client.h
@@ -35,7 +35,7 @@ class CHROMEOS_EXPORT SystemClockClient : public DBusClient {
   // Removes the given observer if this object has the observer.
   virtual void RemoveObserver(Observer* observer) = 0;
   // Returns true if this object has the given observer.
-  virtual bool HasObserver(Observer* observer) = 0;
+  virtual bool HasObserver(const Observer* observer) const = 0;
 
   // Sets the system clock.
   virtual void SetTime(int64 time_in_seconds) = 0;