Or they're just using NativeClient as the sandboxing mechanism.
Equally, its interesting to read that you can register a nativeclient as a plugin for Chrome to be used in their speech api. Not for speech per say, it demonstrates that the connection and the code exists to make it easier to hook into other aspects.
"Extensions are free to use any available web technology to provide speech, including streaming audio from a server, HTML5 audio, Native Client"
https://code.google.com/chrome/extensions/dev/experimental.t...