Check permission for FLAG_WILL_BE_FOREGROUND.

This flag is only designed to be used by platform internals, such as
DownloadManager, so require that callers hold a nice strong
permission.

Bug: 26571724
Change-Id: Ie5ec55399e2e3a64b2837ef2c0a7a8a79bd1e49f

services/core/java/com/android/server/job/JobSchedulerService.java

@@ -1339,6 +1339,11 @@ public final class JobSchedulerService extends com.android.server.SystemService
                         + " not permitted to schedule jobs for other apps");
             }
 
+            if ((job.getFlags() & JobInfo.FLAG_WILL_BE_FOREGROUND) != 0) {
+                getContext().enforceCallingOrSelfPermission(
+                        android.Manifest.permission.CONNECTIVITY_INTERNAL, TAG);
+            }
+
             long ident = Binder.clearCallingIdentity();
             try {
                 return JobSchedulerService.this.scheduleAsPackage(job, callerUid,