Update Gesture navigation page to support search.

Make function public to be reused in SettingsGoogle. Add feature flag.

Bug: 294858168
Test: manual
Change-Id: I3c3ba6144303f21ae4f6da3a64e0208ab23a7382
diff --git a/src/com/android/settings/core/FeatureFlags.java b/src/com/android/settings/core/FeatureFlags.java
index 1a97ca9..fb552d7 100644
--- a/src/com/android/settings/core/FeatureFlags.java
+++ b/src/com/android/settings/core/FeatureFlags.java
@@ -30,4 +30,6 @@
     public static final String CONTEXTUAL_HOME = "settings_contextual_home";
     public static final String SETTINGS_SEARCH_ALWAYS_EXPAND =
             "settings_search_always_expand";
+    public static final String PRESS_HOLD_NAV_HANDLE_TO_SEARCH =
+            "settings_press_hold_nav_handle_to_search";
 }
diff --git a/src/com/android/settings/gestures/SystemNavigationPreferenceController.java b/src/com/android/settings/gestures/SystemNavigationPreferenceController.java
index ab83a9d..ccdb257 100644
--- a/src/com/android/settings/gestures/SystemNavigationPreferenceController.java
+++ b/src/com/android/settings/gestures/SystemNavigationPreferenceController.java
@@ -52,7 +52,8 @@
         }
     }
 
-    static boolean isGestureAvailable(Context context) {
+    /** Returns {@code true} if gesture is available. */
+    public static boolean isGestureAvailable(Context context) {
         // Skip if the swipe up settings are not available
         if (!context.getResources().getBoolean(
                 com.android.internal.R.bool.config_swipe_up_gesture_setting_available)) {