Move mOnSubscriptionsChangeListener to FgThread

Bug: 332451908
Test: on device
Change-Id: I226654fbe8798eced17d82a26c3eab25fa605d87

location/java/android/location/flags/location.aconfig

@@ -78,6 +78,13 @@ flag {
     bug: "314328533"
 }
 
+flag {
+    name: "subscriptions_listener_thread"
+    namespace: "location"
+    description: "Flag for running onSubscriptionsChangeListener on FgThread"
+    bug: "332451908"
+}
+
 flag {
     name: "gnss_configuration_from_resource"
     namespace: "location"

services/core/java/com/android/server/location/gnss/GnssNetworkConnectivityHandler.java

@@ -38,6 +38,7 @@ import android.telephony.TelephonyManager;
 import android.util.Log;
 
 import com.android.internal.location.GpsNetInitiatedHandler;
+import com.android.server.FgThread;
 
 import java.net.Inet4Address;
 import java.net.Inet6Address;
@@ -200,7 +201,12 @@ class GnssNetworkConnectivityHandler {
 
         SubscriptionManager subManager = mContext.getSystemService(SubscriptionManager.class);
         if (subManager != null) {
-            subManager.addOnSubscriptionsChangedListener(mOnSubscriptionsChangeListener);
+            if (Flags.subscriptionsListenerThread()) {
+                subManager.addOnSubscriptionsChangedListener(FgThread.getExecutor(),
+                        mOnSubscriptionsChangeListener);
+            } else {
+                subManager.addOnSubscriptionsChangedListener(mOnSubscriptionsChangeListener);
+            }
         }
 
         PowerManager powerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);