Add one more CategoryKey.

This is used in secondary setting page: App & Notification > AppDefaults

Bug: 31799948
Test: manual
Change-Id: Icc8fa15352006034743c17d2ee943c05a21f612f
diff --git a/packages/SettingsLib/src/com/android/settingslib/drawer/CategoryKey.java b/packages/SettingsLib/src/com/android/settingslib/drawer/CategoryKey.java
index 4ec4f4f..c1f5660 100644
--- a/packages/SettingsLib/src/com/android/settingslib/drawer/CategoryKey.java
+++ b/packages/SettingsLib/src/com/android/settingslib/drawer/CategoryKey.java
@@ -24,6 +24,8 @@
     public static final String CATEGORY_NETWORK = "com.android.settings.category.ia.wireless";
     public static final String CATEGORY_DEVICE = "com.android.settings.category.ia.device";
     public static final String CATEGORY_APPS = "com.android.settings.category.ia.apps";
+    public static final String CATEGORY_APPS_DEFAULT =
+            "com.android.settings.category.ia.apps.default";
     public static final String CATEGORY_BATTERY = "com.android.settings.category.ia.battery";
     public static final String CATEGORY_DISPLAY = "com.android.settings.category.ia.display";
     public static final String CATEGORY_SOUND = "com.android.settings.category.ia.sound";