Add quickUpdate method to BatteryHeaderPrefCtrl

This cl adds a method called quickUpdateHeaderPreference, which will
update the following items immediately without waiting for the
BatteryInfo:
1. Battery level
2. Battery charging status(whether to show lighting bolt)
3. Clear the charging summary

Note: this cl doesn't optimize the BatteryInfo loading time.

This cl also rename "TimeText" to "BatteryPercentText" because in
new UI that textview is used to display battery percentage.

Bug: 63029231
Test: RunSettingsRoboTests
Change-Id: I8cc886b35e937d73b46e47e303ff0994ccdcb61c

src/com/android/settings/fuelgauge/BatteryMeterView.java

@@ -78,6 +78,11 @@ public class BatteryMeterView extends ImageView {
 
     public void setCharging(boolean charging) {
         mDrawable.setCharging(charging);
+        postInvalidate();
+    }
+
+    public boolean getCharging() {
+        return mDrawable.getCharging();
     }
 
     public static class BatteryMeterDrawable extends BatteryMeterDrawableBase {