Allowing system uid to embed Task on secondary user

Settings app was unable to embed task on secondary user
because the uid of Settings was composed with user_id
and app_id, which was not 1000.

Allowing task embedding for system uid on all users.
Also specify the user id while starting activity in
TaskFragments.

Bug: 201738029
Test: start Settings on secondary user
Change-Id: I404379ed049f15abf53084d381c169d3d4cb1166

services/core/java/com/android/server/wm/ActivityStartController.java

@@ -501,6 +501,8 @@ public class ActivityStartController {
     int startActivityInTaskFragment(@NonNull TaskFragment taskFragment,
             @NonNull Intent activityIntent, @Nullable Bundle activityOptions,
             @Nullable IBinder resultTo) {
+        final ActivityRecord caller =
+                resultTo != null ? ActivityRecord.forTokenLocked(resultTo) : null;
         return obtainStarter(activityIntent, "startActivityInTaskFragment")
                 .setActivityOptions(activityOptions)
                 .setInTaskFragment(taskFragment)
@@ -508,6 +510,7 @@ public class ActivityStartController {
                 .setRequestCode(-1)
                 .setCallingUid(Binder.getCallingUid())
                 .setCallingPid(Binder.getCallingPid())
+                .setUserId(caller != null ? caller.mUserId : mService.getCurrentUserId())
                 .execute();
     }
 

services/core/java/com/android/server/wm/ActivityStarter.java

@@ -1979,7 +1979,7 @@ class ActivityStarter {
 
         // Allowing the embedding if the task is owned by system.
         final int hostUid = hostTask.effectiveUid;
-        if (hostUid == Process.SYSTEM_UID) {
+        if (UserHandle.getAppId(hostUid) == Process.SYSTEM_UID) {
             return true;
         }