PreBootBroadcaster.java: Make the PendingIntent immutable

PendingIntents now need an explicit mutability flags. See
go/immutable-pendingintents for more details.

Fixes: 169794258
Test: Green builds
Change-Id: If9268554ecc02acaf08fa62a9a01b5fc6ce374f7

services/core/java/com/android/server/am/PreBootBroadcaster.java

@@ -144,7 +144,8 @@ public abstract class PreBootBroadcaster extends IIntentReceiver.Stub {
 
                     final PendingIntent contentIntent;
                     if (context.getPackageManager().resolveActivity(intent, 0) != null) {
-                        contentIntent = PendingIntent.getActivity(context, 0, intent, 0);
+                        contentIntent = PendingIntent.getActivity(context, 0, intent,
+                                PendingIntent.FLAG_IMMUTABLE);
                     } else {
                         contentIntent = null;
                     }