Fix testcase error

- Because BatteryFixSlice.updateBatteryTipAvailabilityCache() doesn't
run in ShadowThreadUtils shadow function, add a function to override
default behavior.

Fixes: 144405844
Test: make RunSettingsRoboTests
Change-Id: I72ee40a7a8fc524ab7bdc1fd838f8243159f2d21

tests/robotests/src/com/android/settings/testutils/shadow/ShadowThreadUtils.java

@@ -16,16 +16,21 @@
 
 package com.android.settings.testutils.shadow;
 
+import android.util.Log;
+
 import com.android.settingslib.utils.ThreadUtils;
 
 import org.robolectric.annotation.Implementation;
 import org.robolectric.annotation.Implements;
 import org.robolectric.annotation.Resetter;
 
+import java.util.concurrent.Callable;
+
 @Implements(ThreadUtils.class)
 public class ShadowThreadUtils {
 
     private static boolean sIsMainThread = true;
+    private static final String TAG = "ShadowThreadUtils";
 
     @Resetter
     public static void reset() {
@@ -37,6 +42,15 @@ public class ShadowThreadUtils {
         runnable.run();
     }
 
+    @Implementation
+    protected static void postOnBackgroundThread(Callable callable) {
+        try {
+            callable.call();
+        } catch (Exception e) {
+            Log.e(TAG, e.getMessage(), e);
+        }
+    }
+
     @Implementation
     protected static void postOnMainThread(Runnable runnable) {
         runnable.run();