Fix only one battery stat showing sometimes.

Take into account the prefs we are currently caching within the
group when counting how many prefs have been added.

Change-Id: I962acd41592c1a9366882711d3f4944bffb54d22
Fixes: 27931457

src/com/android/settings/SettingsPreferenceFragment.java

@@ -399,6 +399,10 @@ public abstract class SettingsPreferenceFragment extends InstrumentedPreferenceF
         }
     }
 
+    protected int getCachedCount() {
+        return mPreferenceCache.size();
+    }
+
     private void highlightPreference(String key) {
         final int position = canUseListViewForHighLighting(key);
         if (position >= 0) {