Added constructor with looper param for OnSubscriptionsChangedListener

This is needed for tests as subclasses may need to specify which
looper to use.

Bug: 25691379
Change-Id: Ia6eb2d34c439b420ef81622e3c8ff50a0290da22

telephony/java/android/telephony/SubscriptionManager.java

@@ -24,6 +24,7 @@ import android.content.Intent;
 import android.content.res.Configuration;
 import android.content.res.Resources;
 import android.net.Uri;
+import android.os.Looper;
 import android.telephony.Rlog;
 import android.os.Handler;
 import android.os.Message;
@@ -347,7 +348,31 @@ public class SubscriptionManager {
      * for #onSubscriptionsChanged to be invoked.
      */
     public static class OnSubscriptionsChangedListener {
-        private final Handler mHandler  = new Handler() {
+        private final Handler mHandler;
+
+        public OnSubscriptionsChangedListener() {
+            mHandler = new OnSubscriptionsChangedListenerHandler();
+        }
+
+        /**
+         * Contructor that takes in looper as parameter in case a subclass/instantiation needs
+         * to use a specific looper (like in tests where mainLooper may need to be used).
+         * @param looper Looper to be used for mHandler
+         * @hide
+         */
+        protected OnSubscriptionsChangedListener(Looper looper) {
+            mHandler = new OnSubscriptionsChangedListenerHandler(looper);
+        }
+
+        private class OnSubscriptionsChangedListenerHandler extends Handler {
+            private OnSubscriptionsChangedListenerHandler() {
+                super();
+            }
+
+            private OnSubscriptionsChangedListenerHandler(Looper looper) {
+                super(looper);
+            }
+
             @Override
             public void handleMessage(Message msg) {
                 if (DBG) {
@@ -355,7 +380,7 @@ public class SubscriptionManager {
                 }
                 OnSubscriptionsChangedListener.this.onSubscriptionsChanged();
             }
-        };
+        }
 
         /**
          * Callback invoked when there is any change to any SubscriptionInfo. Typically