Create /mnt/pass_through/<userid> in zygote if not created

Similar to /mnt/user, there is a very rare chance that the FUSE daemon
is started before vold mounts the volume, in that rare case, we should
still create the /mnt/pass_through/<userid> dir in zygote before bind
mounting into /storage

Test: manual
Bug: 135341433

Change-Id: Ibb0ee2657b3030ecec8fcef8e447f1fd4548457e

core/jni/com_android_internal_os_Zygote.cpp

@@ -820,6 +820,7 @@ static void MountEmulatedStorage(uid_t uid, jint mount_mode,
   if (isFuse) {
     if (mount_mode == MOUNT_EXTERNAL_PASS_THROUGH) {
       const std::string pass_through_source = StringPrintf("/mnt/pass_through/%d", user_id);
+      PrepareDir(pass_through_source, 0710, AID_ROOT, AID_MEDIA_RW, fail_fn);
       BindMount(pass_through_source, "/storage", fail_fn);
     } else if (mount_mode == MOUNT_EXTERNAL_INSTALLER) {
       const std::string installer_source = StringPrintf("/mnt/installer/%d", user_id);