Set FLAG_IMMUTABLE flag on FirstScreenBroadcast PendingIntent.

Bug: 183927137
Test: restore phone and ensure broadcast is sent
Change-Id: I8d8e38a1aa6bdf13879d460cfa84cabe6c6bb1f2
(cherry picked from commit b62fba0d0199d719ac63761846e09b4b28e1dc2c)
diff --git a/src/com/android/launcher3/model/FirstScreenBroadcast.java b/src/com/android/launcher3/model/FirstScreenBroadcast.java
index 5112304..f9ed2c7 100644
--- a/src/com/android/launcher3/model/FirstScreenBroadcast.java
+++ b/src/com/android/launcher3/model/FirstScreenBroadcast.java
@@ -15,6 +15,8 @@
  */
 package com.android.launcher3.model;
 
+import static android.app.PendingIntent.FLAG_IMMUTABLE;
+import static android.app.PendingIntent.FLAG_ONE_SHOT;
 import static android.os.Process.myUserHandle;
 
 import android.app.PendingIntent;
@@ -145,7 +147,7 @@
                 .putStringArrayListExtra(HOTSEAT_ITEM_EXTRA, new ArrayList<>(hotseatItems))
                 .putStringArrayListExtra(WIDGET_ITEM_EXTRA, new ArrayList<>(widgetItems))
                 .putExtra(VERIFICATION_TOKEN_EXTRA, PendingIntent.getActivity(context, 0,
-                        new Intent(), PendingIntent.FLAG_ONE_SHOT)));
+                        new Intent(), FLAG_ONE_SHOT | FLAG_IMMUTABLE)));
     }
 
     private static String getPackageName(ItemInfo info) {