Don't crash when the load average service is started.

Change-Id: Ie40f549d50942793c940f8728ce9c392c25f4c60
diff --git a/services/java/com/android/server/LoadAverageService.java b/services/java/com/android/server/LoadAverageService.java
index b6baadb..da9fc99 100644
--- a/services/java/com/android/server/LoadAverageService.java
+++ b/services/java/com/android/server/LoadAverageService.java
@@ -278,14 +278,14 @@
             PixelFormat.TRANSLUCENT);
         params.gravity = Gravity.RIGHT | Gravity.TOP;
         params.setTitle("Load Average");
-        WindowManagerImpl wm = (WindowManagerImpl)getSystemService(WINDOW_SERVICE);
+        WindowManager wm = (WindowManager)getSystemService(WINDOW_SERVICE);
         wm.addView(mView, params);
     }
 
     @Override
     public void onDestroy() {
         super.onDestroy();
-        ((WindowManagerImpl)getSystemService(WINDOW_SERVICE)).removeView(mView);
+        ((WindowManager)getSystemService(WINDOW_SERVICE)).removeView(mView);
         mView = null;
     }