Fix the battery icon on the battery page when low battery

Check power-saving state for drawing the battery icon on the battery page.
It will draw red + icon as status-bar did when battery saver is on.

Change-Id: Iee4a17c8e5cb3c8ee5d978eb23e3980597d09a1c
Fixes: 77150820
Test: Manual test, atest BatteryMeterViewTest BatteryHeaderPreferenceControllerTest

tests/robotests/src/com/android/settings/fuelgauge/BatteryMeterViewTest.java

@@ -86,4 +86,11 @@ public class BatteryMeterViewTest {
 
         verify(mDrawable).setBatteryColorFilter(mAccentColorFilter);
     }
+
+    @Test
+    public void testSetBatteryInfo_powerSave_setCorrectly() {
+        mBatteryMeterView.setPowerSave(true);
+
+        assertThat(mBatteryMeterView.getPowerSave()).isEqualTo(true);
+    }
 }