Add a new feature flag for the expand button in support lib.

- check the feature flag to determine whether to use the existing
progressive disclosure mixin or use the expand button in the support
library.
- add corresponding preference xml files that add the new preference
group attribute to use with the expand button in the support lib.

Bug: 63985174
Test: make RunSettingsRoboTests
Change-Id: Ida6eb6182a8066ad1413b7f6142512345fd914d0

src/com/android/settings/DisplaySettings.java

@@ -73,7 +73,8 @@ public class DisplaySettings extends DashboardFragment {
 
     @Override
     protected int getPreferenceScreenResId() {
-        return R.xml.display_settings;
+        return mProgressiveDisclosureMixin.isEnabled()
+                ? R.xml.display_settings : R.xml.display_settings_new_advance_button;
     }
 
     @Override

src/com/android/settings/applications/AppAndNotificationDashboardFragment.java

@@ -60,7 +60,8 @@ public class AppAndNotificationDashboardFragment extends DashboardFragment {
 
     @Override
     protected int getPreferenceScreenResId() {
-        return R.xml.app_and_notification;
+        return mProgressiveDisclosureMixin.isEnabled()
+                ? R.xml.app_and_notification : R.xml.app_and_notification_new_advance_button;
     }
 
     @Override

src/com/android/settings/dashboard/ProgressiveDisclosureMixin.java

@@ -24,6 +24,7 @@ import android.support.v7.preference.Preference;
 import android.support.v7.preference.PreferenceGroup;
 import android.support.v7.preference.PreferenceScreen;
 import android.text.TextUtils;
+import android.util.FeatureFlagUtils;
 import android.util.Log;
 
 import com.android.internal.logging.nano.MetricsProto;
@@ -42,6 +43,8 @@ import java.util.List;
 public class ProgressiveDisclosureMixin implements Preference.OnPreferenceClickListener,
         LifecycleObserver, OnCreate, OnSaveInstanceState {
 
+    @VisibleForTesting
+    static final String FEATURE_FLAG_NEW_ADVANCE_BUTTON = "new_settings_advance_button";
     private static final String TAG = "ProgressiveDisclosure";
     private static final String STATE_USER_EXPANDED = "state_user_expanded";
     private static final int DEFAULT_TILE_LIMIT = 300;
@@ -102,11 +105,17 @@ public class ProgressiveDisclosureMixin implements Preference.OnPreferenceClickL
         return false;
     }
 
+    public boolean isEnabled() {
+        return !FeatureFlagUtils.isEnabled(FEATURE_FLAG_NEW_ADVANCE_BUTTON);
+    }
+
     /**
      * Sets the threshold to start collapsing preferences when there are too many.
      */
     public void setTileLimit(int limit) {
-        mTileLimit = limit;
+        if (isEnabled()) {
+            mTileLimit = limit;
+        }
     }
 
     /**

src/com/android/settings/language/LanguageAndInputSettings.java

@@ -86,7 +86,8 @@ public class LanguageAndInputSettings extends DashboardFragment {
 
     @Override
     protected int getPreferenceScreenResId() {
-        return R.xml.language_and_input;
+        return mProgressiveDisclosureMixin.isEnabled()
+                ? R.xml.language_and_input : R.xml.language_and_input_new_advance_button;
     }
 
     @Override

src/com/android/settings/notification/SoundSettings.java

@@ -109,7 +109,8 @@ public class SoundSettings extends DashboardFragment {
 
     @Override
     protected int getPreferenceScreenResId() {
-        return R.xml.sound_settings;
+        return mProgressiveDisclosureMixin.isEnabled()
+                ? R.xml.sound_settings : R.xml.sound_settings_new_advance_button;
     }
 
     @Override