Update SysUI to use system cache for battery estimates

This should help prevent Settings and SysUI from getting
out of sync with each other.

Test: manual by adjusting battery levels with adb
Bug: 124030091
Change-Id: I8eaba920a10e045c4c983406873de66208c22fb7

packages/SystemUI/src/com/android/systemui/BatteryMeterView.java

@@ -36,6 +36,7 @@ import android.graphics.Rect;
 import android.net.Uri;
 import android.os.Handler;
 import android.provider.Settings;
+import android.text.TextUtils;
 import android.util.ArraySet;
 import android.util.AttributeSet;
 import android.util.TypedValue;
@@ -319,6 +320,9 @@ public class BatteryMeterView extends LinearLayout implements
         mUser = ActivityManager.getCurrentUser();
         getContext().getContentResolver().registerContentObserver(
                 Settings.System.getUriFor(SHOW_BATTERY_PERCENT), false, mSettingObserver, mUser);
+        getContext().getContentResolver().registerContentObserver(
+                Settings.Global.getUriFor(Settings.Global.BATTERY_ESTIMATES_LAST_UPDATE_TIME),
+                false, mSettingObserver);
         updateShowPercent();
         subscribeForTunerUpdates();
         mUserTracker.startTracking();
@@ -493,6 +497,11 @@ public class BatteryMeterView extends LinearLayout implements
         public void onChange(boolean selfChange, Uri uri) {
             super.onChange(selfChange, uri);
             updateShowPercent();
+            if (TextUtils.equals(uri.getLastPathSegment(),
+                    Settings.Global.BATTERY_ESTIMATES_LAST_UPDATE_TIME)) {
+                // update the text for sure if the estimate in the cache was updated
+                updatePercentText();
+            }
         }
     }
 }