Commit 8b11f6a151 requires InitAttributes to be available, which isn't
the case for the secondary context in serialization test. So clone
InitAttributes to make it available.
```
ERROR: JavaScript error: simulation/helpers/Commands.js line 89
InitAttributes is not defined
reveal-map@simulation/helpers/Commands.js:89:7
ProcessCommand@simulation/helpers/Commands.js:932:23
ERROR: Failed to call ProcessCommand() global script function
```
Reported-by: phosit <phosit@autistici.org>
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
4136b2f6f7