chromeos: call GetIdleTime from power manager client

chrome/browser/chromeos/cros/power_library.h

Index: chrome/browser/chromeos/cros/power_library.h
diff --git a/chrome/browser/chromeos/cros/power_library.h b/chrome/browser/chromeos/cros/power_library.h
index 81cb79d7a8e5acb61d8d3185b4033c1215cb9977..a5aa285e718d800a12ff663e10729a0c7b790212 100644
--- a/chrome/browser/chromeos/cros/power_library.h
+++ b/chrome/browser/chromeos/cros/power_library.h
@@ -12,8 +12,6 @@
 
 namespace chromeos {
 
-typedef base::Callback<void(int64_t)> CalculateIdleTimeCallback;
-
 // This interface defines interaction with the ChromeOS power library APIs.
 // Classes can add themselves as observers. Users can get an instance of this
 // library class like this: chromeos::CrosLibrary::Get()->GetPowerLibrary()
@@ -34,10 +32,6 @@ class PowerLibrary {
   virtual void AddObserver(Observer* observer) = 0;
   virtual void RemoveObserver(Observer* observer) = 0;
 
-  // Calculates idle time asynchronously. If it encounters some error,
-  // it returns -1.
-  virtual void CalculateIdleTime(CalculateIdleTimeCallback* callback) = 0;
-
   // Enable/disable screen lock for current session.
   virtual void EnableScreenLock(bool enable) = 0;