Google released the initial Flash Player sandbox for dev channel on Windows XP, Vista and 7.
"This initial Flash Player sandbox is an important milestone in making Chrome even safer. In particular, users of Windows XP will see a major security benefit, as Chrome is currently the only browser on XP that runs Flash Player in a sandbox. This first iteration of Chrome's Flash Player sandbox for all Windows platforms uses a modified version of Chrome's existing sandbox technology that protects certain sensitive resources from being accessed by malicious code, while allowing apps to use less sensitive ones. This implementation is a significant first step in further reducing potential attack surface of the browser and protecting users against common malware," explains Google.
For those already on the dev channel for Windows, you'll be automatically updated soon. If you prefer to disable this initial sandbox in your Chrome dev experience, add --disable-flash-sandbox to the command line.