They mean that you can use Chromium as your primary target — your development stack — and their cross-compiler will take care of supporting legacy/incompatible

They mean that you can use Chromium as your primary target — your development stack — and their cross-compiler will take care of supporting legacy/incompatible targets. This is just like GWT does now and it seems the technology (apart from VM, grammar and debugger) will build on the existing codebase of GWT and the Closure compiler. > What happened to JSPrime? > The JSPrime effort was begun to unify and be a (single!) successor to GWT and Closure/JSCompiler, suitable for large-scale development inside and outside Google, including being amenable to IDE-like tools and static compiler optimizations. The JSPrime team is happily folding its efforts into Dash now that everyone agrees Dash will explicitly include the same goals.