Fix UI flashes issue when entering to the app in the cold start

1. fix the chart % info will flash issue by deferring the showing time
until the chart content is ready to show (set default as invisible)
2. fix the category title will flash issue by set the default value as
empty to avoid refresh the title twice in the start time

Bug: 177406865
Test: make SettingsRoboTests
Change-Id: If8f247cf5b01c529bc5e4d18fcf409ba296cc2f4

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

@@ -157,6 +157,7 @@ public class BatteryChartView extends AppCompatImageView implements View.OnClick
         } else {
             mTextPaint = null;
         }
+        setVisibility(View.VISIBLE);
         requestLayout();
     }