"This release of Chromium with Dart VM integration is a technology preview, and should not be used for day-to-day browsing. After more testing and developer feedback, we plan to eventually include the Dart VM in Chrome," said Google programmers Anton Muhin, Vijay Menon, and Pavel Podivilov, in a blog post yesterday.
The Dart support is in test version of Chromium, the open-source foundation for most of what's in Chrome itself. It's a separate version, though, not released on the main distribution channels for Google's browser. It's available only for Mac OS X and Linux now, with a Windows version "coming soon."