Update battery states text

- Update progress bar bottom text when battery states changed(charging,
 discharging, power saver and low battery)

Bug: 183689347
Bug: 177407113
Test: make SettingsRoboTests
Change-Id: I0397eb1dea7fcb14357750f84d1d5b1a7dc7d19a

src/com/android/settings/fuelgauge/batterytip/BatteryTipPreferenceController.java

@@ -16,6 +16,7 @@
 
 package com.android.settings.fuelgauge.batterytip;
 
+import android.annotation.Nullable;
 import android.content.Context;
 import android.os.Bundle;
 
@@ -162,6 +163,19 @@ public class BatteryTipPreferenceController extends BasePreferenceController {
         return mNeedUpdate;
     }
 
+    /**
+     * @return current battery tips, null if unavailable.
+     */
+    @Nullable
+    public BatteryTip getCurrentBatteryTip() {
+        if (mBatteryTips == null) {
+            return null;
+        }
+
+        return mBatteryTips.stream().anyMatch(BatteryTip::isVisible)
+                ? mBatteryTips.stream().filter(BatteryTip::isVisible).findFirst().get() : null;
+    }
+
     /**
      * Listener to give the control back to target fragment
      */