Fix legacy failed tests to avoid block presubmit

Root cause: the `Robolectric.setupActivity(Activity.class)` is removed from the system, which will always return the null `Context`

Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.fuelgauge.*
Change-Id: Ib52bc715508332bcb4bdcac56ecc414aa43f1419

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

@@ -25,12 +25,12 @@ import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
-import android.app.Activity;
 import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
 
 import androidx.preference.Preference;
+import androidx.test.core.app.ApplicationProvider;
 
 import com.android.settings.R;
 
@@ -39,7 +39,6 @@ import org.junit.Ignore;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.MockitoAnnotations;
-import org.robolectric.Robolectric;
 import org.robolectric.RobolectricTestRunner;
 import org.robolectric.annotation.Config;
 
@@ -52,7 +51,7 @@ public class TopLevelBatteryPreferenceControllerTest {
     @Before
     public void setUp() {
         MockitoAnnotations.initMocks(this);
-        mContext = spy(Robolectric.setupActivity(Activity.class));
+        mContext = spy(ApplicationProvider.getApplicationContext());
         mController = new TopLevelBatteryPreferenceController(mContext, "test_key");
     }