Change to use the expand button in support lib.

- functionality for hiding portions of the preferences in the preference
screen is added to the support lib. So, changing the settings
implementation to use the feature from the support lib instead.
- remove ProgressiveDisclosureMixin and the related code

Fixes: 63985174
Test: make RunSettingsRoboTests
Change-Id: Ib1d39b2db93d78a56c7adf90abcae5226f9564c2

tests/robotests/src/com/android/settings/language/LanguageAndInputSettingsTest.java

@@ -43,7 +43,6 @@ import android.view.textservice.TextServicesManager;
 
 import com.android.settings.R;
 import com.android.settings.TestConfig;
-import com.android.settings.dashboard.ProgressiveDisclosureMixin;
 import com.android.settings.dashboard.SummaryLoader;
 import com.android.settings.testutils.SettingsRobolectricTestRunner;
 import com.android.settings.testutils.XmlTestUtils;
@@ -103,9 +102,6 @@ public class LanguageAndInputSettingsTest {
 
     @Test
     public void testGetPreferenceScreenResId() {
-        ProgressiveDisclosureMixin progessiveMixin = mock(ProgressiveDisclosureMixin.class);
-        when(progessiveMixin.isEnabled()).thenReturn(true);
-        ReflectionHelpers.setField(mFragment, "mProgressiveDisclosureMixin", progessiveMixin);
         assertThat(mFragment.getPreferenceScreenResId()).isEqualTo(R.xml.language_and_input);
     }
 
@@ -173,8 +169,6 @@ public class LanguageAndInputSettingsTest {
         final List<String> niks = LanguageAndInputSettings.SEARCH_INDEX_DATA_PROVIDER
                 .getNonIndexableKeys(context);
         LanguageAndInputSettings settings = new LanguageAndInputSettings();
-        ReflectionHelpers.setField(settings, "mProgressiveDisclosureMixin",
-                mock(ProgressiveDisclosureMixin.class));
         final int xmlId = settings.getPreferenceScreenResId();
 
         final List<String> keys = XmlTestUtils.getKeysFromPreferenceXml(context, xmlId);
@@ -186,8 +180,6 @@ public class LanguageAndInputSettingsTest {
     public void testPreferenceControllers_getPreferenceKeys_existInPreferenceScreen() {
         final Context context = RuntimeEnvironment.application;
         final LanguageAndInputSettings fragment = new LanguageAndInputSettings();
-        ReflectionHelpers.setField(fragment, "mProgressiveDisclosureMixin",
-                mock(ProgressiveDisclosureMixin.class));
         final List<String> preferenceScreenKeys = XmlTestUtils.getKeysFromPreferenceXml(context,
                 fragment.getPreferenceScreenResId());
         final List<String> preferenceKeys = new ArrayList<>();