[13] RFR: 8020637: Permissions.readObject doesn't enforce proper Class to PermissionCollection mappings

[Sean Mullan]

It is currently possible to change the mappings in a serialized 
java.security.Permissions object such that they no longer map correctly, 
and Permissions.readObject won't detect this.

This change makes sure that for a deserialized Permissions object, the 
permissions are mapped correctly to the class that they belong to. It 
does this by calling add() again for each permission in the deserialized 
Permissions object. The same technique was applied to a serialized 
PermissionsHash object which is used to store Permissions that don't 
implement their own PermissionCollection.

bug: https://bugs.openjdk.java.net/browse/JDK-8020637
webrev: http://cr.openjdk.java.net/~mullan/webrevs/8020637/webrev.00/

Thanks,
Sean