> Performance has absolutely nothing to do with sand boxing. Even simple optimizations like shared caches fall afoul of proper isolation. In the past browser c

> Performance has absolutely nothing to do with sand boxing. Even simple optimizations like shared caches fall afoul of proper isolation. In the past browser caches could be abused to find out if a user frequented specific sites just by checking how long it would take to request a site specific resource. Result: no more shared caching, all resources had to be loaded for each site separately.