Right, if you can do that, why not stick NaCl + Android Runtime for Chrome on everyone&#x27;s cell phone? NaCl is designed to be very low-overhead, and low-end Chromebooks are probably as underpowered as low-end phones.<p>NaCl is a very good isolation layer, but it&#x27;s certainly possible that to make Android apps work &#x2F; interoperate the way you&#x27;d expect (e.g., one app can broadcast an intent that another app can receive), you have to open up holes that are too big to secure. It&#x27;s sort of like how the CPU-level distinction between kernel-mode and user-mode code is a very good isolation layer, but when you run actual operating systems that need their processes to communicate, it gets much harder to secure.